Glad you asked! Music Production. Only possible on iPhone as the latency through android is about 40-80ms, not optimal. Plus, doing a quick search in the playstore reveals lack of any music creation apps ever. iOS gets GarageBand, Cubasis 3, moog synths, Audio Units Extensions, sampling and granular synthesis, anything you can think of or want is available on iPhone. And anything you can’t get on iPhone is a matter of time. The music production software for iPhone can get you so much further, budget wise than buying a Mac or PC where the equivalent software is $50-$2,000. An iPhone app costs Maximum $50 in the music space. I’ve only seen the strings sample library cost more. It’s insane for the portability, budget, and sheer power you’d get over anything else. Plus one day you can jailbreak it and do whatever you want.