A gyroscope measures orientation based on gravity. An accelerometer measure motion based on acceleration and velocity. Magnetic sensor's allow the Earth's magnetic field to be used as a reference.

Read more: http://venturebeat.com/2012/11/27/forget-six-axis-gamepad-nine-axis/

I think Nintendo Land is using best in class 9-axis motion controls on Wii U. That DK Crash Course for sure... any other games using it?