Other companies are extremely interested in utilizing the technology behind the third party accessory, Wii MotionPlus.
“I can’t get into details about other folks that are interested in this technology, but as you might imagine of course there is more interest out there.”
The clip-in Wii peripheral adds a “MEMS (micro electrical mechanical systems) rate gyroscope” to the Wiimote. This allows rotation around the X, Y, and Z axes produced by the accelerometer.