Developers have combined a Kinect and Windows Phone to create a holographic game engine. It was posted on Engadget and they explain it well:
If your life is anything like ours, it’s in sore need of more pseudo-holographic helicopters. Fortunately, YouTube user programming4fun has come up with a solution, using Microsoft’s Kinect beta SDK and a Windows Phone handset. The system, pictured above, basically consists of a Kinect and a 3D engine; the former tracks the position of a viewer and automatically adjusts the image projected by the latter, creating the illusion of a 3D landscape. In this case, that landscape happened to feature a holographic helicopter, which could be controlled using a phone’s accelerometer and a Windows Phone 7 app (apparently called HoloController). Watch it in action, after the break.