For my final computer science project this year, I decided to make a math competitions tracker, since I wish I had something like this when I first started doing competitions last year. There are two main features of this app:
Playground - this is where you will find checklists for all of the major math competitions out there
Courses - another set of checklists for math competition books, but for fun, you have to 'buy' a course with the coins you get from completing problem sets in the playground
As of right now, all of the user data is stored locally, but I will try to connect it to some online database sometime in the future.
Since my layout was quite responsive, this app also runs fine on the web. You can find them here (different links but the same app...), but be careful not to delete the cookie saved in your web browser because all of the data is stored there.