TechBitar wrote the Ardudroid app (for Android only as far as I’m aware – Sorry iPhoners – but I’m sure the creative macintosh users will have made an equivalent… somewhere).
Ardudroid allows you fo control your microcontroller very effectively in many ways, accessing many pins. It would be very good to get familiar with it so that you can begin to control things with it (e.g. motors, lights etc)
This video introduces, made by TechBitar himself the Ardudroid app (using BT): https://www.youtube.com/watch?v=USeZd9jthZM
P.S. It would be nice to program our own apps. The software is freely available, but I don’t have the time to do it. But if YOU do have the time, then you might want to download MobinCube (Android, Apple or Windows OS’s !!) Here’s a tutorial guide by Omkar Jadhav to tell you how to hold your hand in getting things going… https://www.youtube.com/watch?v=bBt_5tofOlc