Thanks Jun. Looks interesting both sites. A little different to what I have in mind, but they should have some good information. One of the things I have in mind is to combine this with the rigid body physics engine like used in games, so that you can play with parameters such as size and weight differences between uke and nage.
Jean, I believe the phrase "because we can" applies here
At least in my case it is for personal interest, that I have access to such equipment for no cost, and it's already what I do for work. The basic difference between a video and these is that you can take any vantage point you like and turn on/off any feature you like. For example, tracing the footwork rather than the motion of the hands - just turn off the bodies and leave the foot prints.
The same question applies to books - why would anyone want to buy a book when the only way to learn is to do it? People like information in different ways. Pictures help, maybe a computer-based simulation will too. For example the Tae Kyan site in Korea is doing something very similar, teaching people the very old martial art there that contributed a lot to TKD and Hapkido kicking techniques.