How we choose products

Last updated: 2026-05-11.

This page is the methodology behind every "best fitness tracker" or "best sleep tracker" list on BasisScience. We've kept it short so you can spot when we've deviated from it.

The criteria we score against

1. Sensor accuracy under real conditions. Wrist-PPG heart rate validated against a chest strap during steady-state and HIIT. SpO2 compared against a finger pulse oximeter at rest. Sleep staging compared against the published Oura/Withings-validated benchmarks where applicable. We do not claim clinical accuracy; we report drift.
2. Real-world battery life. Manufacturer claims are optimistic. We score what we measure, with always-on display where applicable and our typical workout schedule.
3. Data ownership. Can you export your raw data without paying? Is there a documented API? What happens if the company shuts down the cloud? The Basis Peak failure mode is a hard requirement we screen for.
4. Subscription dependency. What works without paying monthly. What gets paywalled. Any product that paywalls basic metrics earns a flag.
5. Cross-platform support. iOS, Android, and the existence of a web export.
6. Build, fit, and comfort. Subjective. We try to wear test for at least 30 days where possible, including overnight.
7. Privacy posture. Default sharing settings. Whether health data is sold to insurers or marketers. Whether there's a documented data-deletion path.
8. Total cost of ownership over three years. Sticker price + subscription + accessories.

How testing actually runs

For every product in a buying guide, at least one of:

• We've worn it for 30+ days personally, including overnight.
• We've tested it against a chest strap and a reference oximeter for at least three workouts.
• We've consulted a peer-reviewed accuracy study and the manufacturer's regulatory filings.

If none of the above apply, the product is not in our top picks. It may appear in a "we have not tested this; here is the spec sheet" section, clearly labeled.

What disqualifies a product

• It's been recalled and the recall remains active.
• It's been discontinued and the cloud or app has been shut down (the Basis Peak case).
• It has known sensor accuracy problems documented in peer-reviewed work that the manufacturer hasn't addressed.
• It paywalls fundamental metrics behind a subscription that wasn't disclosed at purchase.
• The manufacturer makes overt medical claims without regulatory clearance.

How rankings change

We re-test our top picks at minimum once a year, and after any major firmware update (Fitbit OS, Garmin Connect IQ, watchOS major versions). When a ranking moves, we note the reason in the changelog. We do not move a product up because the affiliate commission rate went up, and we do not move a product down because we got a better commission rate from a competitor.

If you think we got it wrong

Email editor@basisscience.com or use the contact form. We read everything.