Just for those that want an alternative to the GoPro (~$275.00), I bought a refurbished (couldn't tell it wasn't new) Kodak Zi8 HD video recorder from Newegg for $74.99. It records up to 1080p and stereo sound. Take a look and see what you think!
http://www.youtube.com/watch?v=Kf-zP9gh47U
Did a test with and without external mic.
Sorry for my big head in the rearview, didn't notice it until I got home and looked at the video. (Was having too much fun driving!)