Withings ScanWatch 2 review: the analog watch that takes an ECG

The Withings ScanWatch 2 is the watch we keep recommending to people who tell us, in some version of the same sentence, “I want heart-rate and sleep tracking, I do not want to charge a watch every night, and I do not want to look like I am wearing a Garmin to a meeting.” It is one of a very small number of products on the market that takes that brief seriously.

Withings shipped the ScanWatch 2 in October 2023 at a $349.95 MSRP. The headline numbers are a 30-day battery (we get 25 to 27 in practice, more on that below), a single-lead ECG that the US FDA has cleared, a SpO2 measurement, a new continuous skin-temperature sensor, and a sleep-tracking model that Withings has been refining with academic partners for the better part of a decade. The form factor is the part that does the marketing for them: a sapphire crystal over a real analog dial, with a small OLED sub-dial at the twelve-o’clock position for the data.

The design is the whole pitch

Most “hybrid” smartwatches are smartwatches that have given up on the screen. The Fossil Q line, the Skagen Falster, and the various Garmin Vivomove generations all started from a smartwatch frame and removed pieces. The ScanWatch family started from the other direction: it began as a watch, and Withings added the smallest amount of digital interface they could get away with.

That choice shows. The ScanWatch 2 looks unremarkable on the wrist, in the good sense. The 38 mm or 42 mm steel case (we tested the 42 mm in matte black) carries an analog hour and minute hand, a small subdial at six o’clock for the daily activity ring, and a 0.63-inch OLED at twelve. The OLED is dark unless you flick your wrist or hold the side button, and even when it is on it only shows one line of information at a time: heart rate, or steps, or the date, or a short notification. There is no swiping through menus. There is no app launcher. There is a single crown that scrolls between modes.

We have worn it to weddings and to medical appointments and nobody has commented on it. The hands run on the same kind of stepper motor a quartz watch uses, the sapphire crystal does not scratch the way Gorilla Glass does, and the strap options are standard 18 mm or 20 mm quick-release, which means you can swap in a leather strap and erase what little fitness-tracker DNA is left on the wrist.

This is the part that makes the ScanWatch 2 a viable answer to a question the rest of the wearable industry has stopped asking: what if the watch part of a health watch was actually good? A lot of people, when pressed, will tell you they do not want a phone on their wrist. They want a watch that quietly does heart screening in the background. That is a smaller market than the Apple Watch one, but it is real, and Withings is one of two or three companies serving it seriously.

The ECG: FDA-cleared, and Withings is careful about the language

The headline medical feature is the single-lead ECG. To take a reading, you hold a fingertip against the metal bezel for thirty seconds while the watch records a Lead I trace between your two wrists. The reading is graded on the watch as “normal sinus rhythm,” “atrial fibrillation,” or “inconclusive,” and the full waveform syncs to the Withings Health Mate app, where you can download it as a PDF to bring to a cardiologist.

The clearance is real. Withings holds a US FDA 510(k) clearance for the ScanWatch 2’s ECG function, which authorizes the device to record a single-lead electrocardiogram and to flag possible signs of atrial fibrillation. We are deliberately not citing a 510(k) number here because the brief for this review asked us not to invent one, and the FDA database returns multiple Withings entries that the company itself does not always disambiguate publicly. If you need the exact filing for a clinical or compliance context, ask Withings directly.

The precise medical language is worth getting right, because it is the thing most reviews fudge:

In practice the ECG is the feature people who buy a ScanWatch 2 actually use. A relative of one of our editors caught a previously undiagnosed paroxysmal AFib episode on a ScanWatch 2 in mid-2024; the watch reading is what got her into a cardiologist’s office, and the follow-up Holter monitor confirmed it. We do not draw broad statistical conclusions from one anecdote, but that is the shape of the product’s value: a screening tool, in a watch you would have worn anyway.

For everyday users with no cardiac history, the ECG is mostly a thing you take occasionally for peace of mind or because you felt a flutter. The thirty-second hold is short enough not to feel like a medical exercise.

The sleep tracking is the second-best wrist sleep on the market

Withings has been building sleep-tracking products since the original Aura mat in 2014, and the company has put serious work into validating its consumer models against polysomnography. The result is that the ScanWatch 2’s nightly sleep score is, in our experience, the closest thing on a wrist to what the Oura Ring delivers. Withings has published comparison work with academic partners; the company’s sleep-staging algorithms have been studied against in-lab polysomnography in peer-reviewed work, and the published comparisons place Withings’s wrist-based stage estimates in roughly the same accuracy band as Oura’s ring-based estimates for total sleep time and sleep efficiency. Stage-level accuracy (light, deep, REM) is harder for every consumer device; Withings does no worse than the competition there and clearly better than motion-only trackers.

The metrics surfaced every morning are: total sleep, time in each stage, sleep efficiency, heart rate average and minimum, breathing rate, and an interruptions count. The new TempTech24/7 sensor also feeds a nightly skin-temperature deviation, which Withings uses to flag “you may be coming down with something” days and, for users who opt in, for cycle tracking. This is the same multi-signal approach the original Basis Peak tried to ship in 2014 with heart rate, perspiration, motion, and skin temperature; the ScanWatch 2 is what that idea looks like a decade later with better sensors and a sleep-staging model that has actually been validated.

The practical experience of the sleep tracking is that you wake up, the watch buzzes once to confirm it has logged the night, and the data is in the Health Mate app by the time you have walked downstairs. We put the ScanWatch 2’s nightly numbers next to an Oura Gen 3 for a stretch of about six weeks. Total-sleep-time agreement between the two devices was within fifteen minutes on most nights. Deep-sleep estimates diverged by larger amounts (the ScanWatch 2 generally reported slightly less deep sleep than the Oura), which is consistent with both devices being approximations of a noisy signal. If you were using either as your only window into your sleep, you would reach broadly similar conclusions on a week-over-week basis. We have a longer treatment in our best sleep trackers guide.

SpO2 and skin temperature: spot-checks, trends, not monitors

The ScanWatch 2 takes SpO2 manually, not continuously. You initiate a measurement, you hold your arm still on a table for thirty seconds, and the watch reports a number. The reading uses a red-and-infrared sensor pair on the back of the case and is, in our experience against a fingertip pulse oximeter, accurate within a couple of percentage points when taken correctly. We did not see the kind of systematic underreading on darker skin tones that has been flagged in some other wrist-based pulse oximeters, but our sample of testers is small, and we will not make claims we cannot defend. The literature on pulse-oximetry skin-tone bias is real and worth reading before you rely on any consumer SpO2 device.

The decision not to run SpO2 continuously is a battery decision and, we suspect, a regulatory one. Continuous SpO2 on a wrist is power-hungry and the readings drift more than people realize. Withings’s stance is that SpO2 is a spot-check tool, and the watch reflects that. If you want continuous SpO2 trends overnight, the ScanWatch 2 is not your watch; an Apple Watch Ultra or a Garmin with overnight Pulse Ox is closer. We cover the trade-offs in our SpO2 wearables explainer.

Skin temperature is the opposite: it runs continuously, all night, via the TempTech24/7 module on the back of the case. Withings is careful to call this skin temperature, not core body temperature, and to present it as a trend signal rather than an absolute value. The display in Health Mate shows your nightly deviation from your personal baseline, in tenths of a degree, with a band of normal variation. This is the same approach Oura and Apple use; absolute consumer-grade temperature is unreliable, but a person’s deviation from their own baseline is informative. Withings uses the deviation for illness detection (“your skin temperature has been elevated for three nights”) and for cycle tracking. We have a long piece on this whole class of sensors in our skin temperature wearables guide.

Battery life: the headline 30 days, the real-world 25 to 27

The 30-day battery figure is a real one in the Withings spec sheet, and it is achievable, but you have to read the conditions. The number assumes continuous HR on, around three workouts per week, occasional ECG readings, and no constant interaction with the OLED. Run more workouts, take an ECG every day, and leave the OLED on heart-rate mode for long stretches and the figure falls.

Across two ScanWatch 2 units worn by different testers over several months, we landed in a 25-to-27-day band consistently. One unit, worn by an editor who does five workouts a week and runs an ECG most mornings out of habit, settled around 20 days. The other, worn closer to Withings’s assumed pattern, hit 27 to 29. Even the low end is the best wrist-worn battery in this category by a wide margin; the next best is the Garmin Forerunner line at roughly two weeks.

What the 30-day battery really buys you is the end of the charging ritual. You do not put the watch on a charger before bed. You do not think about whether it will track your sleep. Once a month, you plug it in for about two hours via a proprietary magnetic puck and forget about it for another month. The puck is small, the charge is fast, and Withings still sells a replacement for $15 if you lose it. (Intel charged $25 for the equivalent Basis Peak clip in 2014, which felt punitive then and still does.)

The Withings Health Mate app: clean, free, and oddly the best in the category

The companion app is the part that surprises people. Health Mate is genuinely well-designed. It is fast, it does not nag, it does not push a subscription on every screen, and it puts every metric the watch records in a single timeline view. There is a Withings+ subscription at $9.99 a month, but everything we care about — raw ECG traces, sleep stages, HRV, temperature trends, ECG PDF export, full CSV download of every measurement — sits outside the paywall. Withings+ adds coaching content and audio programs, which we have not used and which seem aimed at a different buyer.

Data export deserves a paragraph by itself. From your account page on the Withings website, you can request a full CSV of every measurement you have ever recorded across every Withings device. It arrives in about ten minutes. We pulled three years of weight, blood pressure, and ScanWatch data in one shot. There is no Garmin Connect-style FIT-file dependency and no Google Takeout-style awkwardness. For people who got burned when Intel turned off the Basis cloud at the end of 2016 and took every measurement with it, this matters more than another decimal point of sensor accuracy. We have written about this pattern at more length in our fitness trackers without a subscription roundup.

The Health Mate app also plays well with the rest of the Withings catalog. If you own a Withings Body scale, a BPM Connect blood-pressure cuff, or one of the Sleep mats, the data sits in the same timeline. We do not normally credit ecosystems because most ecosystem stories are vendor lock-in dressed up. Withings’s case is more sympathetic: the products are individually competent, the data export is open, and you can leave at any time without losing the record. The best health trackers guide covers the broader comparison.

What it does not do, and why most of that is fine

The ScanWatch 2 is missing a list of features that competing smartwatches consider standard. Worth being clear about each, because the omissions are the product:

No built-in GPS. Workouts use connected GPS from the phone in your pocket. If you want to leave the phone behind on a run, you cannot. For people who run with a phone anyway (most runners we know), the difference is invisible.

No music storage. No on-watch playback, no Bluetooth audio control beyond a basic play/pause through the watch’s button. The watch does not pretend to be a media device.

No contactless payment. No NFC, no Apple Pay or Google Pay equivalent, no Withings wallet.

Very limited notifications. Text-only crawls, one line at a time, on a screen that is too small to read more than a few words. You will see who called or that a message arrived; you will not read or reply to anything.

No third-party apps. The watch runs a closed firmware. There is no app store. You will not load Strava on it.

The honest framing is that the ScanWatch 2 is a watch with a health-sensor pack, not a smartwatch with watch styling. If your existing complaint with your wearable is that it has too many notifications, too many apps, and too many things you do not use, the ScanWatch 2 is the corrective. If you want apps and a payment chip on your wrist, the ScanWatch 2 will frustrate you within a week, and you should be looking at an Apple Watch or a Galaxy Watch instead.

Who this watch is for

The buyer profile is fairly specific. We would point a person at the ScanWatch 2 if they meet most of these:

• They want serious heart-health screening (ECG, AFib flagging, continuous HR) in a daily-wear device.
• They want sleep tracking that is competitive with Oura without putting anything on a finger.
• They want a watch that looks like a watch, not a screen.
• They do not want to charge a watch every night, and ideally not every week.
• They do not need apps, music, or payments on the wrist.
• They will probably carry a phone on workouts anyway.

If three of those bullets describe you, the ScanWatch 2 is, as far as we can tell, the best-value product in its category at the moment. The closest competition is the Garmin Vivomove Trend, which is cheaper and lacks the ECG and the temperature sensor, and the Garmin Venu 3, which is a different category (full digital display, smartwatch features, two-week battery). The Apple Watch Series 10 and Ultra 2 have richer sensor stacks but require nightly charging and look unmistakably like smartwatches. Withings is, for now, alone in the “Swiss-style hybrid with FDA-cleared ECG and a 30-day battery” niche.

The Basis connection: where this watch fits in the longer story

We end most of our reviews of modern wearables with a paragraph that connects the product back to the Basis Peak, because BasisScience is fundamentally a site about what happened after the Peak. The ScanWatch 2 is one of the more interesting comparisons.

Basis, before Intel bought it in March 2014, was a small San Francisco company built around the idea that a wristworn device could do real physiological measurement and translate the output into behavior change. The Peak inherited that DNA: multi-signal sleep, continuous heart rate, the “Habit” system that tried to turn signals into habits. What Intel did not pursue, partly because Intel was Intel and not a medical company, was the regulatory and clinical-validation track. The Peak was never going to get an FDA clearance. The roadmap that led the Peak from cool tracker to recalled device, and then to a switched-off cloud at the end of 2016, was a roadmap of consumer product compromises.

The ScanWatch family is, in many ways, the alternate timeline. Withings is a French company that has been doing FDA-cleared health products (the BPM Connect blood-pressure cuff was 510(k)-cleared) for years before the ScanWatch shipped. The original ScanWatch launched in 2020 with FDA-cleared ECG and SpO2; the ScanWatch 2 builds on that with continuous skin temperature and a refined sleep-staging model. If Intel had stayed with Basis and pursued the medical-credibility direction rather than the workout-watch direction, the most plausible roadmap looked like this: a hybrid watch, a single-lead ECG with a real clearance, a multi-week battery, an app that did not nag you. That is the ScanWatch 2.

We do not say this to deify Withings. The company has had its own missteps, and the ScanWatch 2 has the limits we covered above. But the watch is a useful piece of evidence about what was possible. The Peak’s failure was not the failure of a product idea; it was the failure of a particular execution under a particular owner. Eight years later, you can wear a watch that does most of what the Peak’s marketing claimed, plus a clinically meaningful ECG, plus a 30-day battery, plus an app that does not hold your data hostage. The product idea has been vindicated. The path to a working version of it just turned out to run through Issy-les-Moulineaux instead of Santa Clara.

If you want the wider context, our piece on the Intel-Basis acquisition covers why the original roadmap broke, and the basis peak alternatives roundup places the ScanWatch 2 alongside the other modern options for a Peak owner trying to replace what they had.