Elliptic Labs has some interesting technology on display here in Barcelona. The company says it can add gesture-based controls to smartphones and remove several hardware components at the same time. According to VP Guenael Strutt, hardware makers are clamoring for just such a solution. Less hardware means less clutter in phone designs, and less internal space needed for those components, and, of course, less overall cost.
Elliptic Labs says sound waves are the answer. The company's software emits ultrasonic sound waves (in the 44Khz neighborhood) through the earpiece or speaker that are then picked up by the microphone. These high-hertz sound waves are very pressure sensitive and can be used to measure distance quite easily. Come within range (which can be tuned, but is generally within a foot), and you can use various gestures to perform select actions.
For example, bring your hand close to a phone's screen to unlock the phone or dial up video controls. It can also interact with games. The tech can be installed in other objects, such as lights or radios, permitting users to turn these devices on and off by waving their hands in front of the device. It's sort of like The Clapper, but for the age of the connected home.