Reversing Camera
I also bought one off ebay, about £70 for a colour camera with a 4" colour monitor (but no sound) superb, however you DO need good reversing lights for it to work in the dark (or a nice illegal 55w fog lamp!) There are now cameras with built in LED's to light the area but I don't know how good they are. My only concern is... will Billy Burglar realise it's just a cheap monitor on the dash, and NOT a fancy LCD TV (with a DVD player mounted somewhere)?
I now put the Silver screens up every time I park in the street, a bit of a pain; but I've not lost a side window YET!!