Smart Alarm is a privacy-focused sleep tracker with powerful features. It's an open source project, which works without an internet or phone connection.

Note: you need to install this application from your watch! It will display as incompatible on your phone.

Among its features are:
- Sleep detection (light, deep, REM) and statistics
- Accelerometer and Heart Rate tracking
- IFTTT integration
- Smart Alarm (with snooze)
- Export data to email address
- Auto-export
- Adjustable tracking (no HR? Poll less often? No problem!)

This app is in active development - feature requests and feedback is appreciated!

Documentation: https://www.github.com/fridgecow/smartalarm/wiki
Source: https://www.github.com/fridgecow/smartalarm
Server Source: https://www.github.com/fridgecow/smartalarm-server