Apple was just awarded a whole mess of patents by the USPTO. But one stands out in particular: a 3D display and imaging system. Wave your hands and the system picks up your movement. Sort of like the Xbox Kinect. Or, uh, exactly like the Xbox Kinect.
The system described in Apple's patent would use a projector with a scanning beam that picks up your movements via a receiver, shown as a secondary device. Your movements are transferred to the system and a user can interact in a virtual space using their body as their only input device:
To be effective, it is also important that such devices be capable, when desired or necessary, of economically but effectively and precisely providing feedback to the user. Thus, such devices should incorporate audio and/or visual mechanisms for reporting to the user the effects and results of the 3D input.
Apple does point out that the projector could be used to show holographic imagery, something the Kinect doesn't currently do—well, officially anyway. Think Minority Report meets Kinect.