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.
iPad apps you wish were on iPhone
Maybe I'm not thinking this through. There are obviously some interfaces that just won't work out well. The first one I went for was iM1. Seems like the only way to get it on iPhone is to download Gadget. Usability is probably the biggest issue for me and I'm not even sure how well iM1 would fare. Mela 2 is done pretty well but I still don't really like it all squished in.
Please feel free to discuss.