As hans said, the wii is very good for starting up "sensor/accel" projects. Although when you need better data the wii will not provide, so don't raise much expectations.
At my research lab we work with accel+magnetometer to correct the values, anyhow it is now wireless for now, which is a major disadvantage of the current setup. The previous one was a wireless accelerometer-based from Plux (http://www.plux.info/) with a C++ API.
Best of luck, Pedro