Today I have been hacking away on the iphonearkit source available at github and have incorporated the ARGeoViewController as an overlay over a ImagePickerController with the camera as the source (which was introduced with iPhone OS 3.1). Results below.
I want to tidy up some of the code before I check it back into my clone of the source, but this is a really good basis for some smart location and direction aware augmented reality apps on iPhone. Wonder what the iphonearkit license is - it's unclear...
--- EDIT ---
Bugger. It appears that zac has implemented similar functionality to me already :-( Bloody github and it's slow (never!) updates to fork queues and network graphs. Oh well, maybe I won't bother tidying my code.