The one in the Jag I am looking at will only work when the car is in park, or if it is turned towards the passenger side so as the driver can not see it. Personally it would be for DVD use mainly on long journeys (to keep the nephews and nieces quiet) or boring waits in car parks, also I would be tempted to use it as a screen for a reversing camera like the mates Lexus has, and he has even put another camera inside very like the ones the police use (and some insurance companies) not unlike this:
http://www.dogcamsport.co.uk/reversing-camera.htm