Regarding apps I prefer to program for Android and general use Android Studios.
Math Ninja Master
Android Studio and LibGDX
I made a game with the intent of teaching kids another way to think of math. It was filled with platforms and arithmatic. Using standard controls the player would jump on platforms and it would change the player's number with a end platform that requires that the player's number is correct.
Table Occupation Scanner
Android Studio
A project that I pursued but is incomplete. Its purpose is to check occupancy and is done by scanning QR Codes. The idea is for it to help people look up whether or not there are open tables and to keep track of the hours where the most tables are occupied.