Somthing that would totally make me cream myself on the spot would be a screen where for at least each pixel there would be a distance sensor (kinda like Project Natal's camera but the imaging sensor instead of being a grid behind a lens it would be a grid the size (and resolution) of the screen laid on the screen itself)

Of course, also detecting multiple touch pressure with assorted materials like Stantum's would rock. Hell, since i'm dreaming high, gimme also one of those baterryless wireless Wacom stylus with 1024 levels of pressure sensitivity on the tip and two side buttons, popping out of the device itself like the N900's stylus.