no... because mobile in gets the audio I/O from the dock connector which is higher quality than the standard mic input that would be used for a headset (bluetooth or not)

I can't see how "It should be able to work I believe..." can be the "correct" answer to anything.  If you can't test it then you don't know, and as a Line 6 representative you should be more careful about posting misinformation.  I purchased the Mobile In, and tested with several paired Bluetooth devices.  It DOES NOT work - at least not with the Line 6 Mobile Pod application.  On an iPhone 4, guitar input ceases to register as soon as Bluetooth is paired.  On an iPad (1), guitar input and audio output activity are visible on screen (via the meters) but an audio signal is never transmitted - instead, it continues to route to the 1/8" out despite the Bluetooth pairing.

If there's another app that works, I'd love to hear about it.  If there's a patch for Mobile Pod, I'd love to hear about it.  But the answer in green is NOT correct.