Apple recently filed a patent that makes touch controls disappear -- literally. The patent (No. 8,303,151) is for something called "microperforation illumination," and while the name is catchy, the technology is actually rather complex.
First you pick a non-display surface of a device like a laptop. For this example, let's just say the top of the laptop's lid. Then, using microperforations in the surface itself, you pass light through the material, making a shape appear. Combining this idea with touch controls means you could soon have "invisible" buttons that appear when in use, but disappear promptly afterwards.
But the patent goes beyond just the idea of invisible controls. There is also the mention of varying sizes and shapes of microperforation, and even tiny lenses that could control the flow of light from one side to the other.
However, as with all patents that make us raise an inquisitive eyebrow, there's no clear indication of what product, if any, might incorporate this rather interesting feature.