The Wii MotionPlus is an expansion device for the Wii Remote video game controller for the Wii that allows it to capture complex motion more accurately. According to nintendo, the sensor in the device supplements the accelerometer and Sensor Bar capabilities of the Wii Remote to enable actions to be rendered identically on the screen in real time.
The Wii's successor console, the Wii U, supports the Wii MotionPlus and its peripherals in games where
use of its touchscreen-built-in primary controller is not necessary.
