iOS 6.0 brought "multi-route audio" support to the iPhone / iPad.
DJay app for example benefits of it by allowing the user to hear one deck in headphones while playing the other.
The only mention of it is in the AVAudioSession class reference :
AVAudioSessionCategoryMultiRoute Allows you to output distinct streams of audio data to different output devices at the same time. For example, you would use this category to route audio to both a USB device and a set of headphones. Use of this category requires a more detailed knowledge of, and interaction with, the capabilities of the available audio routes.
This category may be used for input, output, or both.
Available in iOS 6.0 and later.
How to route two distinct streams to different routes ? Especially using Remote I/O ?
Thanks!