I bought on ebay a license plate light with camera for a Fiat Punto. They are $24.
It fits where our license plate light goes (you retain the light). Then drill a small hole in the trunk and connect the camera to a small wifi transmitter also available on ebay for about $35. Wire the power for the transmitter and camera to the license plate light. When I need the camera I turn on the lights, find on the wifi signal on my Iphone and see the screen on the downloaded app. Works great and easy to install.
Launch Edition 4C