Pushing the envelope
In the interests of being an awkward cuss and stretching things further than they're supposed to go...
Say I have an instrument on my iPad which isn't really playable on my iPod, and I want to play it out through a non-Audiobus fx app on my iPod and take it back into Audiobus on the iPad to record into one of the Audiobus recording apps. I would have to a) use two iRigs or similar, b) split the headphone out from my iPod so I can hear what I'm playing and c) be able to mute the recording app so that only my instrument app presents audio to the iPad output.
Anyone think of a good reason why that wouldn't be possible?