ANT is a proven wireless sensor network protocol and silicon solution for ultra-low power networking applications in sport, wellness, home and industrial automation.
Operated on world-wide licensed-free 2.4GHz ISM band
Micro-watt power consumption (Approx. 4 years of battery life on a 2032 coin cell when sending a message every 2 seconds, 24 hours per day)

By reading the gyro data of the new wii motion plus peripheral with the arduino microcontroller, we are able to create a 6 DOF IMU for under $40