Envy posted a question about using his iPhone .. one of the links in that thread shows a grip for like-$80. Looks well done, but I'm not sure I'd expose my $$$ phone to the potential abuse, tho' this rig looks pretty good.
If you have a nano laying around, this one works: http://www.rampantgear.com/ I bought one. It's a decent item. The nano's video is nothing like a Canon 7D, but ...if you already have one? ..this is only $35 more.
http://www.youtube.com/watch?v=wLg7QSMQ3Vk&feature=results_video&playnext=1&list=PL60089C1A50BDC469 ...an example of why you have to remember there's a camera on your head is well on display here.