They can probably already do the "no touch" proximity thing now. From what I've heard, the iPhone's screen uses a capacitance method of sorts, detecting the electrical energy/field from your finger. If you could make that detection process more sensitive, it would be reasonable to think that you wouldnt' have to come into contact with the screen if it can detect your finger at x millimeters away. Then again, I'm a mechanical engineer so I don't know much about the electrical side of things.

I guess it might be harder (and more expensive) to implement such a system on a large display as shown in the video though...