This promotion video started with the phrase "Introducing a New Way to Play" but please make sure you have checked the last part of the video. It may become a new way to communicate, a new way to use digital devices (PC, TV) and eventually a new way to live. It seems like a futuristic video but you can see the stage demonstration in E3 in the video below.
The technology behind this is the depth-sensing camera. Normal camera will just give us pixel value of a 2D plane, depth-sensing camera however provide an extra dimension which is the depth of the pixel value. It is done by sending out Infrared pulses and measuring the time the reflected pulses being received later, just like how radar works. 3DV Systems will be releasing a low cost depth-sensing camera very soon.
The Wiimote hacker Johnny Chung Lee is one of the man behind the project Natal, read more from here. He is the man that inspire a lot of people to start the Wiimote-based DIY projects on interactive whiteboard, virtual reality display, gesture-based interaction.