I have this:
http://www.amazon.com/Angle-Mobius-A.../dp/B00GPXYVQU
Great quality camera that is small and cheap (1080p at 18MB/s, as good quality as a GoPro3)
hardwired into mirror, turns on with car, turns off 30s after car, 32GB card fits about 4hrs of looping video with my settings.
It has some motion detect feature, but I've never tried it