I've been using them in my Computer Eng. Problem Solving class for 3 years.
Here's a vid where freshmen measure a drop (accounting for air resistance) using a wiimote.
I'd say they make a great instrument as long as you quantify your error.
If done right, the game or whatever just serves as an engagement and recruiting tool. The important bit is then using the platform to introduce problem solving and programming learning opportunities and then relating that back to the non-gaming IT world.
In my case, I teach the first course in Computer Engineering, and I use the Wii Controller as the data source. Check out http://www.youtube.com/watch?v=tPCBfyQP4eE to see a lab where students use the wii remote in a foam football to measure the distance it fell in real time in an 8+ meter drop.
This draws on their physics, math, and learning how to structure solutions to a problem nicely.
Basically, 9 years ago we showed some remarkably embarassing features in Xerox multifunction printer/copiers/faxes. Including SNMP access to plaintext passwords!
I wonder how many of these "features" are still there.