Nintendo announced the Wii MotionPlus at the E3 2008 just in time to take away attention from the Microsoft E3 briefing.

Nintendo Wii MotionPlus accessory for the Wii Remote controller redefines game control, by more quickly and accurately reflecting motions in a 3-D space. The Wii MotionPlus accessory attaches to the end of the Wii Remote and, combined with the accelerometer and the sensor bar, allows for more comprehensive tracking of a player’s arm position and orientation, providing players with a higher level of precision and immersion.

Every slight movement players make with their wrist or arm is rendered identically in real time on the screen, providing a true 1:1 response in their game play.
Nintendo will reveal more details about the Wii MotionPlus accessory and other topics Tuesday morning at its E3 media briefing.
Via the Nintendo site.