Plees Tracker is a simple sleep tracker for your Android phone.
The latest version is v6.2, released on 2020-05-08. See the release notes.
This is meant to be a very simple open source clone of PrimeNap, i.e. just track sleep start/stop times and count the average / day.
It literally does nothing while you sleep, causes no battery drain.
Stores past sleeps, counts stat from them:
average of sleep durations
daily average: in case you sleep multiple times a day or you sometimes skip a whole day
Exports/imports sleep data to/from CSV (the start and stop columns are UNIX timestamps in milliseconds).
Can show past sleeps, can selectively delete individual sleeps.
It looks like this:
Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.