It seems like we these "health researchers using Wii in study" stories about once a month but, anyway, Oxford University, last I heard, was a pretty good school. And they're looking at the Wii as a means to help stroke patients relearn simple tasks.
The study is a little more subtle than other research involving the Wii (training surgeons, for example) -- the motion sensors might be useful for monitoring patients' progress in physiotherapy. Apparently, one of the biggest challenges patients face is constant discouragement from not being able to see, or really understand, the progress they're making. The motion sensors can also tailor exercises to a patient's range of motion.
The research is based on a previous study in which motion-capture technology was used to analyse the walking patterns of children affected by cerebral palsy. The Wii's sensors offer a scalable way to examine and monitor patients. It's envisioned that patients would first be examined using a full-camera setup in a lab, and then switch to a home monitor that incorporates cheaper motion sensors such as those found in the Wii. There's a video of this at the link below.
This isn't the only instance of consumer technology leading the way in other fields of serious research. Not by a long shot. For example, my favourite Nobel Prize winner, Dr. Carl Wieman of the University of British Columbia (formerly Colorado), used diode lasers like those found in CD players to help create the first Bose-Einstein condensate in 1995. Sometimes, you send a guy into space and get back Teflon, Tang, Velcro and Dippin Dots. And sometimes you develop Wii Sports and get back new forms of therapy.