Here's the best meditation app I've found.
https://meditationapp.wixsite.com/download-app/copy-of-privacy-policy
It's extremely privacy-conscious (no personal information required). I personally like the minimalistic approach, with focus on the essential, i.e.:
1) A configurable timer
2) A diary
3) Reporting
The app has a few minor bugs, but hardly noticeable and reproducible, and because the development seems to have stopped a few years ago, it probably means they won't get fixed anymore.
If you are thinking of starting a regular sitting practice, or need motivation with your current practice, I strongly recommend you give it a try. It is free of charge (the dev accepts tips), and, even more importantly, free of ads!