I would just like very briefly to the sleep function Tracking: it works simply not. It measures far too optimistic, the deep sleep phases. I had months recorded with Sleep as Android and this app diagnosed me only a small deep sleep phase (about 50%) For comparison, now I have a Pebble, Sleep as Android and make the Samsung Activity Tracker to record a night at the same time. Pebble and the Android app were very close to each other with the measurement result (45% / 52%), while the Activity Tracker has shown 92% deep sleep. So I can only suspect that the Activity Tracker measures wrong, a great pity.