Chinese martial artists have noticed that it’s no longer possible to practice tai chi or kung fu in parks as used to be the case in China. So they’ve collaborated on developing a program called Tai Chi Master that uses the camera in your computer to film you, and give you feedback, while you use the screen to follow the movements.
Here’s another link to the demonstration of the program if the video doesn’t properly embed.
Update: OK. It appears that it’s not actually a real program available yet, but it is a really cool idea, akin to Neo/Keanu Reeves waking up in the Matrix and knowing Kung Fu.