[knuckles904] was able to use the new Wii MotionPlus with an Arduino. Nintendo has released the WM+ in order to detect the motion of the controller better. The Wiimote only detects acceleration, whereas the WM+ detects rotation along 3 axes. The Arduino communicates with it over I2C, the same protocol that is used with the Nunchuk. To connect the two devices, he used jumper wires, but breakout boards are also available. He was able to create some example code with help from wiibrew.org. When paired with a Nunchuk, which contains a 3-axis accelerometer, you can have a 6 degrees-of-freedom IMU for under $40, perfect for controlling your robots or logging data.