I love using iOS Apps to make music, my favorite is Figure by Propellerhead. I make loops in there and plug in my Apple iPad Pro into my Macbook Pro through my Apogee Duet Audio Interface and then route the audio into Ableton when I want to play Live. It's wonderful, this is a powerful machine it's a full blown computer. I use it for multitasking a lot too! It works well with side-by-side data entry and whatnot, you can even edit sound clips on it with Audio Copy & Audio Paste! It's wild.
With Ableton Link, menubus, & internal MIDI, it's become an inspiration even if the tracks never make it into my work. I feel it's a lack of imagination on my behalf tho. I'll be exploring further as time allows but yeah-the iPad is now an instrument. A ton of 'em. I'll update w/ the instrument apps as I explore. Definitely not to be discounted, even if it's not your bag. Lord knows I never thought it'd be part of my stuffs.