For a couple of years we have been mounting HD GOPROS and various camcorders and even a Sony NEX under our main DSLRs--we love the intimate video:
http://www.youtube.com/watch?v=--_NJ_pE77M
here're some stills of the mount for shooting stills and video at the same time:
http://www.flickr.com/photos/herosjourneymythology45surf/sets/72157632670975563/
we've been wondering when will photographers start mounting gopros and other cameras on their dslrs to capture video throughout the shoot? we've been trying such things for a couple years with amazing video results! we call it 9shooting or 45surfing with a 9shooter or 45surfer :)
the less we edit the video, the more our fans love them, as it takes them to the photoshoot. :)