I tried SleepAsAndroid and they quality of the measurements is low (on my mid-range smartphone).
Less anecdotal: The German computer magazine did a comparison of many sleep Apps including a comparison in a sleep laboratory. Poor guy needing to sleep with all those devices in bed. The result was that the fancy curves as mostly way off the only reliable thing is start and end of sleep.
I tried SleepAsAndroid and they quality of the measurements is low (on my mid-range smartphone).
Less anecdotal: The German computer magazine did a comparison of many sleep Apps including a comparison in a sleep laboratory. Poor guy needing to sleep with all those devices in bed. The result was that the fancy curves as mostly way off the only reliable thing is start and end of sleep.
Here it is: http://www.heise.de/ct/ausgabe/2015-25-Schlaftracker-vs-Schlaflabor-2910003.html