At its simplest level this concept could work by mimicking the four way compass pad on a car player, Central, or receiver, translating touches in the top, right, left & bottom of the screen, and perhaps the centre of the screen for enter. More complicated gestures like tracing out a play symbol to make it play, or worse still a FFWD symbol to seek, then a pause symbol to stop it seeking would probably lead to more 'hands off the wheel' time than the deep & populated menus resulting from minimal controls. Also, the user would still have to look at the screen to position their finger in the right place.

Actually, I think one could do this without having the user looking at the screen, if you use true gesture recognition instead of mapping different screen section to certain commands. User would then just touch their way to the screen and do their gesture command, for which it doesn't matter if it's on the right half of the screen or on the left.

Directions would be mapped to a single finger tap + slide. Tap one finger and slide it right to ffwd. In a sense this creates a even more natural feeling, because the finger can go faster over the 2-dimensional sensor array or slower. So there's a direct relationship between action and command. Just like a dial does feel more natural for volume adjusting than constant speed (or even accelerated) up/down buttons. Now traditional touchscreen sensing technologies can only track motions of a single finger, but if it would feature one of these multitouch arrays we could map a two-fingerslide to a skip. Again, by moving two fingers slow and a just a bit to the right we skip one track. Fast and/or further to the right for skipping several tracks, while speed of motion determines how far the fingers have to slide to skip one track. The faster the shorter it is. This would enable you to 'accelerate' ...in a way. Two fingers up/down slide could be ... vol up/down.. Tap a single finger without sliding to play. Tap two pause....whatever.. you get the idea.

That being said, I still think knobs, dials, and buttons are the better solution for a car. Above gesture recognition does well for a HID ,allowing to map copy/paste, alt-f4 and the like shortcuts to gestures, but it doesn't provide the tactile feedback I'd like to have in a car situation.