cameras

but seriously, you know hte small "back up" cameras you see some people put on (not factory) there cars taht sit on the license plate? take that small camera, hide it anywhere. be creative. then, instead of it going to a screeen, you can buy things to make it saved to a card or whatever

20$ back up camera
http://www.ebay.com/itm/TAOTRONICS-W...item20c0220523

small camera

http://www.ebay.com/itm/New-3-5-LCD-...569294&vxp=mtr

another. they all have the cables that would plug into a source for saving on a card.
http://www.ebay.com/itm/CAR-Night-Vi...item41625b49c5