Howsit,
I bought one recently. Its not a high end dash cam but it does its job. It records HD video up to 720p. Uses micro SD so storage capacity will depend on the size of the SD card you put in. Its a dual lens camera so you can set it up to record the inside of your car or the rear of your car while it is recording the front.
The camera connects to your cigarette lighter so you can set it up yourself. If you want to have the rear camera installed permanently then you might need to get someone to assist with running the cable to the rear windscreen.
See attached pic of the camera, I got the pic off the web.
I will post my setup later. I got this to play around with, hence I did not go for the top end brands like GoPro. It will depend on how much you want to spend.