Audiobus: Use your music apps together.
What is Audiobus? — Audiobus is an award-winning music app for iPhone and iPad which lets you use your other music apps together. Chain effects on your favourite synth, run the output of apps or Audio Units into an app like GarageBand or Loopy, or select a different audio interface output for each app. Route MIDI between apps — drive a synth from a MIDI sequencer, or add an arpeggiator to your MIDI keyboard — or sync with your external MIDI gear. And control your entire setup from a MIDI controller.Download on the App Store
Audiobus is the app that makes the rest of your setup better.
Things iOS lacks
Although iOS music production is far from being in its infancy, there's definitely areas that remain unaccounted for. I'm curious to know what one thing people feel is still missing from their own iOS setup.
For me personally it's something like Madrona Labs' Virta:
An AUv3 effects lab that processes things in what I can only describe as a kind of Buchla-ish way. The closest I've got to this is using iVCS as a sample processor, which gives some fantastic results, but isn't quite what I'm after. Obviously, an ideal outcome of this post would be somebody saying "ah, but X does this!" (not just for my identified area of lack, of course, but for everyone's). Anyway, have it: what is missing for you?