Today I went through my things looking for a device with composite video output, since that is (in 2012!) the input the display in my Seat Altea XL understands. The only and yet so fitting thing I could find was my Raspberry Pi. I installed Raspbmc (an XBMC specially prepared for the Raspi) on an sdcard, plugged the audio and video cables into the car, added power through a 12V adapter in the car and booted away. The result can be seen in the pics at the end. The Raspi doesn’t need much power (~0.7-1.0A), stays cool and has no movable parts, making it perfect for usage in a car. Of course if you don’t connect audio to the car, you can just use headphones instead so you could watch something in the back while listening to music on your cars stereo. (Preferably deactivate sound on the speakers in the back, but that isn’t a problem.) Next thing on my list is a remote. I have a ATI/X10 USB remote lying around somewhere, that is supposed to work out of the box.