I was thinking about the Child of Eden demo that has been shown, and it struck me that the game uses hands/arms for aiming and shooting, and it almost seems as if the hands are opened/closed. You can see quite a bit of detail in the point cloud representation that is shown in 3D in the fitness game, and this got me wondering whether Child of Eden is perhaps using more detailed information from this point cloud to focus just on the hands, rather than using the default full body frame information that most games use? It looked interesting and natural for such a huge screen, but if you'd do the same thing in front of a small screen that would invite the user automatically to use much smaller movements, which could be a problem.
The point cloud may be splodgy, but it can be quite detailed, if you looked at that scene in the fitness game demonstration, where you could see the garment that was taken off and was pretty faithfully replicated all the way until it hit the ground.