In June, Nintendo will be releasing a peripheral called MotionPlus. This small device attaches to the bottom of the Wii-mote and acts as a more sophisticated motion-sensor to the controller as it currently stands. Its goal is to bring greater parity between a user's movements and the animations that they bring to life on-screen. Gameplayer got some hands-on time with the device, and they are extremely impressed."
The MotionPlus will only affect new games; Nintendo has said they have no plans to add support for older titles. Virtua Tennis 2009 will be the first game to support it, and Eurogamer has a look at the game both with and without the MotionPlus.

http://games.slashdot.org/article.pl.../04/20/0549241