All of those things except presence detection can be done by tapping one key or another. For example, most computers have keys for controlling music players, they're just not integrated properly. As the article says, it feels a bit silly to wave you hand in front of the screen what you can just move your finger a couple of inches from whatever you were doing and achieve the same result with a lot less energy.

If we worked like Tom Cruise does in The Minority Report, we'd have a far bigger problem than carpal tunnel syndrome.

But maybe we could use something like this to bring mouseover effects back to tablet computers? Hover your finger above a button and watch it spin before you tap it!