After all the recent patent interest in touch screen control methods, a new front is deverloping over touch free controls.
Both Apple and Microsoft have filed patents regarding controlling devices without physical contact, and others such as Qualcomm and Extreme Relatity 3D are also filing applications in the space.
While Apple envisage users being able to 'throw' content from one device to another, Microsoft describe sculpting 3D objects with hand gestures.
Touch-less control is not as new as it may sound, apart from a striking resemblance to a scene in the film Minority Report, Sony launched gesture recognition in their eye-toy based computer games in 1999, laser harps have been on the stage since 1981, and sci-fi favourite stalwart the Theremin was patented in 1928 (and who does not want to play with a Theremin?).
Microsoft have a good starting point in this area, with its already proven Xbox Kinetic accessory (in turn build on Rare(UK) and PrimesSense(Israel) technology).
Kenetic has proved a hit in the games space, and is impressively accurate, however its also expensive (relying on a infa-red laser depth sensor, in addition to camera), and bulky. Adapting it to be usable on a phone will be a challenge.