Have you looked at keychain cameras? The video quality is OK (720p 30fps) and they are very inexpensive, on the order of ~$20-$30 for a cam with a memory card.
I had a bad experience with a keychain camera a year ago - it would randomly stop recording and the video quality was horrible.. However, I found a few models on ebay that do 720p like you said that look a lot nicer than what I had previously. There is also a mod that will allow me to run a switch to the dash to start/stop recording. The particular cameras that can do this are $38 shipped (Its called the 808 #16), and the rest of the parts needed are $5 per camera approx (usb cable, 5v adaptor, microcontroller). Theoretically I can get three views - front, rear, and pedals - for $129. Not bad.