I don't know if this add-on to PS2 is known about in Japan, but it has been released in the UK and is very popular. The game that comes with it has taken the number one slot in gaming charts for a couple of weeks.
The technology has been around for years. I went to a Sony TechnoFair which shows new technology for Sony employee's only, this was about 4 years ago. Then, they had a camera rigged up and using PS2 processing via USB, it would recognise motion of hands, etc of someone infront of the camera.
It seems this product with the games has been developed in the UK, hence being released early. I've heard that it's great fun for parties.
A link to a review on the product;
http://www.pocket-lint.co.uk/games/reviews/review80.htm
For no real reason except to have a bukkake emoticon