GoForSmoke:
Or you can use a (mini/micro) joystick or touch-area with white at center and shades all around.
That's an interesting idea. However, many joysticks (even the miniature ones) are designed to self center and even those that don't can't be counted on staying in position with all the movement to be expected in a car. Therefore, you'd either have to have one with a button action, or a separate button. That would allow control logic like press the button once to read the position of the joystick, then press it again to save it.