Update: Check out this video demo!
I posted a thread on the Open Music App Collaboration (OMAC) Google Group on switching between apps using a MIDI controller. The idea was originally inspired by Rheyne, who usually uses more iOS devices in his live looping jams than most iOS users have. I thought that if there was a way to switch between iOS apps from an external source (a MIDI controller), using your multiple apps on one iPad live would be easier. The 4/5 finger gesture switching can press buttons or turn knobs, and double tapping the home button to open the multitasking menu is too much of a hassle (in a live setting).
Nic G from Audeonic Apps has proposed a strategy to accomplish this but we need an “I’m in” from a reasonable amount of developers before it gets implemented. If you’re a developer and would like to add this to your app, check out Nic G’s proposal here.