Last year for Christmas I received a Vivitar 2800 flash and a Sun-Pak Digital Camera Flash Adapter. The adapter utilizes the flash with any camera that has a built in flash. It mounts to the camera via the tripod screw and the flash mounts to the adapter--a lot like a vertical grip set up. Both the flash and the adapter require AA batteries but there is no actual connection to the camera. It fires the flash like a slave flash. Several modes on the bracket.
I've used this flash with Panasonic, Olympus and my current Sony A100 and I've been satisfied with the results each time. I've never heard of this type a of bracket adapter on any of the forums but it certainly seems to be a good auxillary flash set up. I was wondering if anyone else has any experience with this type of unit.