Wii MotionPlus

Wii MotionPlus is an accessory that is placed at the bottom of the Wii Remote (where the Nunchuk expansion is usually plugged into). For greater use, the Nunchuk can also be plugged into the bottom of the accessory. It, in Nintendo's words, supplements the accelerometer and Sensor Bar, and allows for exact actions to almost be replicated perfectly in the game.

History
It was announced on July 14, 2008, a day before Nintendo's E3 2008 press conference. During the conference, they showed off the device along with Wii Sports Resort, a game the accessory would come packaged with. Also accompanying the device is a longer Wii Remote jacket so that it covers both the remote and the Wii MotionPlus.

During E3, Wii Sports Restort producer Katsuya Eguchi explained that Nintendo could possibly in the future create Wii Remotes with this funcionality already built into it.