I've got a boyo and like it, and installed a few others like exonic. IMO, the amount of time that you are going to be viewing it, get whatever you can.
Since I have a wall in my jeep, this is what I use for my rear view mirror on an 8" screen. The color is not real good, but where these cheapie camera's do excel is during night use. They work in total darkness pretty well. I paid $30 for one on ebay.