I wrote an app (MIKME) which does this - the apps purpose is to allow remote recording with a self-powered bluetooth microphone, so you can have "point-source"

I wrote an app (MIKME) which does this - the apps purpose is to allow remote recording with a self-powered bluetooth microphone, so you can have "point-source" audio for your video projects - leave the microphone with the subject, but move the camera around.. It wasn't that difficult to get audio/video in sync .. I just used AVFoundation, which has plenty of functions for dealing with the sync issue. The biggest problem was getting the recordings off the microphones filesystem to the iOS device - we had to invent a new protocol for this ("lost and found protocol"), because Apple sure don't make it easy for devices to share data .. but once the files are copied, the sync is the easy part.