NAV-TV has a solution if you are looking to add a Backup Camera to your Porsche Cayenne -
The PCM3.1 is a fully automatic backup camera interface for 2011 and Up Porsche Cayenne. It also works on the 2009 and Up Porsche Panamera.
A second camera, such as a FLIR night-vision, front or interior (child) camera, can also be added to the vehicle with the purchase of an additional video switcher, and manually selected on the PCM screen.
However, this second camera will not operate while the vehicle is in motion; to have a second camera that operates in motion requires the PCM3-AV970 kit.