Yeah, I don't really see any issues regarding liability. Its one thing if the system starts saying "YOU HAVE CANCER AND WILL DIE IN A WEEK" - when you definitely don't - that would cause legal problems ;)
But the Wii would be "soft" in terms of wording .. things like "You health is poor", or "You may want to consider more exercise and a better diet", etc.
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As for the Japanese toilets - that sort of thing may be part of the reason the Japanese are one of the healthiest nations in the world. I was talking to a friend here, and she let me know that Australia has now overtaken the US in terms of "per-capita fatness" (using body/mass ratios and other tests) and is now effectively one of the least healthy (non-3rd world) countries in the world.
I agree with Kwaad, in that it will depend heavily on how "good' the system is. Blood pressure tests? Heart rate? Body temperature? Do you manually enter your height, weight, etc?
I can see something like a pulse/heart rate monitor working? - in conjunction with some basic exercises (so it measures your effective fitness by how well your body adapts to exercise, etc).
Gesta Non Verba
Nocturnal is helping companies get cheaper game ratings in Australia:
Wii code: 2263 4706 2910 1099