On the subject of dash cams which sounds like a good idea, is is feasible easily to swap such a camera from one car to another? Reason for asking is that they appear to have the need for a power supply cable and I'm not sure how easily the cam can be connected/reconnected.
I have the Transend Drive Pro, you can get a rubber suction attachment thats allows you to move it from car to car and it plugs into the power socket. Works day and night.