Disclosure: #FitbitEmployee but I don't speak for Fitbit. Any Fitbit with heart rate will give you maximum acccuracy according to https://www.wareable.com/fitb

Disclosure: #FitbitEmployee but I don't speak for Fitbit. Any Fitbit with heart rate will give you maximum acccuracy according to https://www.wareable.com/fitbit/fitbit-sleep-tracking-defining-feature-6496 https://www.wareable.com/fitbit/fitbit-sleep-tracking-defini... Heart rate is key to getting good sleep stages data, so a non-wearable won't do. https://blog.fitbit.com/heart-rate-during-sleep-stages/ https://blog.fitbit.com/heart-rate-during-sleep-stages/ To integrate with Apple HealthKit you need a 3rd party app.