I run one of the top music apps in the game called Rapchat which lets users record raps over beats and share them with friends. Our goal @ Rapchat is to mobilize the hip hop world by allowing anyone to create, share, and discover freestyle raps.
In addition to Rapchat, I've been a freelancing iOS dev for 2+ years and also just launched a course on CodeUpStart that teaches people how to code a clone of Snapchat from scratch.
Objective-C is still my language with plans to pick up Swift in the near future.