This app was mentioned in 6 comments, with an average of 4.50 upvotes
Use QuietMind for android. It is free, quality, beautiful, and most importantly minimalist.
Set a time to meditate, start, then hear a ding.
...
...
Ding Done.
Even the tracking is very simple only looking at how many of the last 7 days you have meditated.
Have you heard about QuietMind on Android? It's made by a redditor (/u/ragoneio) and for me it's already the perfect companion app for TMI. And it's even open source! You should get in touch with them.
https://play.google.com/store/apps/details?id=ragone.io.quietmind&hl=en_US
I use QuietMind. Very simple app that's a timer plus it shows your meditation streak and gives you the ten stages of meditation from Culadasa's The Mind Illuminated, so you know what level you are at and progressing too.