As far as I\'ve been able to tell, whenever you override an audio route in the iPhone, you have to change both the output AND input routes together. The only available route
After talking with Apple engineers on the Coreaudio mailing list, I've found it's not currently possible to do this with a single RemoteIO audio unit.
I'm going to try to instantiate two audio units, one for playing, the other for acquisition, but I'm not hopeful. We shall see.