Stephen Eaton has been working on a wireless, low voltage Arduino for camera trigger applications: Strobit. After a call to geekdom in 9/2007, the project has gotten to the point that boards have been manufactured and are being tested.
The project page at Gcode has lots of information, there are photo sets on Flickr-- board development progress and some photos taken using prototypes-- and an Arduino Forum thread with a few questions answered. I continue to be impressed by the level of sophistication people have been putting into their Arduino-compatible boards.
