Tracker Showdown: Which Wearable Wins for Sleep?

Most consumer sleep trackers, including the ones detailed in our chart, use a combination of physiological signals (such as: heart rate, heart rate variability, respiratory rate, skin or core temperature, and movement) to algorithmically estimate your sleep stages (light, deep, REM), duration, and quality. They are only able to estimate. They do not provide direct measurements of brain activity, and their accuracy often varies. Something as seemingly irrelevant as a person’s skin tone or movement patterns can occasionally affect a sleep tracker’s accuracy.