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 StoreAudiobus is the app that makes the rest of your setup better.
Gigging with iOS
From what I've read in other threads some of you use iOS apps & peripherals in live shows. A friend if mine who has been building his home studio wants to get into that sort of thing eventually & one of the things he wants is to be able to do is sample the group while they play live & then loop that sample back while the group moves off into more esoterica (solos, other musical extravaganzae, etc.).
So, what apps & iOS peripherals are best suited to explore this sort of thing? Loopy comes to mind right away but I don't yet have it (it's on the wish list) so I have only a meager idea of its capabilities. I would think others have applications here as well.