What an interesting idea.

All sorts of images spring to mind, but none of them relevant, and some of them obsene.

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. At times like this I always remember Fabris describing his 'groping for the nipple' procedure for using an empeg remote whilst driving in the dark. In the same way, you could 'grope for the knob' whilst keeping your eyes on the road with the current Camelot design, but tracing out a decrease volume symbol would certainly require more attention.