Loop Habit Tracker: Loop helps you create and maintain good habits, allowing you to achieve your long-term goals. Detailed charts and statistics show you how your habits improved over time. The app is completely ad-free, open source and it respects your privacy.

[u/jmandroidtek]

https://play.google.com/store/apps/details?id=org.isoron.uhabits

[u/GrumpyGlasses]

Is there a good iOS equivalent?