RE:Using video games for weight loss
DDR and it's spinoffs are definitely good tools for weight loss/fitness, as well as a fun and addictive source of entertainment. I remember during the peak of the big DDR craze the local arcade had a huge celebration for its leading customer's 3000(!)th game, and this was only the game's third month or so in the arcade.
I also remember quite a few of the repeat patrons getting noticeably slimmer month in/month out. Tech TV even had a spotlight on a girl that lost near 100 pounds while using DDR as a big part of her regime.
I myself had never used DDR as a weight loss device, but repeat games really helped out with my coordination and rhythm for TKD. If you have access, I would definitely recommend buying a DDR pad/game kit for the house, saves a lot of quarters and chuckles from onlookers in the long run, and makes a good source of entertainment at gatherings and such, even for nongamers.
Sony has also put out a webcam type accessory, called the eyetoy, that i would recommend checking out, with a lot of cool games that get Your butt off the couch and into the action.
And then of course there's always the old track and field and dance games for the NES
Okay, well enough geekiness for now, I think You get the idea.
-Nick