Some explanations of the device base it on a simple echo of light: "The camera transmits invisible near-infrared light and measures its “time of flight” after it reflects off the objects. Time-of-flight works like sonar: If you know how long the light takes to return, you know how far away an object is." (wired.com). Is it so easy? On other hand, the developers, Primesense, speak about "a sophisticated parallel computational algorithm to decipher the received light coding". And they claim to avoid noise from ambiance light and to be able to obtain a resolution of 1cm at 2 meters.
A motivation to ask this here in physics is that some other questions were asking for measurement of light speed with household devices.