This app was mentioned in 1 comment, with an average of 2.00 upvotes
There are a few apps available though they are often in German. Maybe take a look and do an English version?
They are used for tracking symptoms and scheduling exercise.
It really depends on your goals of the app.
https://play.google.com/store/apps/details?id=de.interactive_systems.msdiary
https://play.google.com/store/apps/details?id=de.teva.copaktiv