TV/DVD into Sat nav screen?

I am looking to move up from my X to an S-Type and want to get one with the built in touch screen sat nav. Is it possible to wire up the sat nav screen so it can display DVD or  TV input? Or would a better optio be to buy an aftermarket unit with the sat nav / dvd etc already built in?

It's posible, hell yes,  I just don't know how? Check out this S-type he has tv on his OEM navi. There's a few on cardomain.com http://www.cardomain.com/ride/721163/4
 
You could even mess around and get something like this.  http://www.cardomain.com/item/BRACMM08F    http://www.cardomain.com/item/BRACMP657 

Thanks, yes the in car computer looks great. I know you can get factory TV as the car is an R would think this may be factory fit.

Rivs keep me updated, as I would like to get my OEM navi to play dvd's. Eventually, I would aslo like to add a back up camera.

instead of paying that much for the in car computer, u cud just get a touchscreen screen, and then add a laptop with the rite software. Itll be cheaper if u already have a laptop, and plus ull be able to do more with it. But for the TV and dvd playing, in sure its something as simple as connecting a dvdchanger, or a tv tuner to the video input cables (may require cutting into existing wires). Ive never done this, its just an assumption. Wud be sweet to have it on the factory nav. hope it goes well.