In EyeToy: Groove the player must hit targets with their arms on the edges of the screen to the beat of the music.
The game also includes a built-in calorie counter which estimates calories burned based on the player's weight. Players can usually burn around 5-20 calories per song. There are rewards available for high amounts of calories burned. There is also a mode that allows players to design their own moves for the songs.
Building on from the 'Beat Freak' mode from Eyetoy: Play, players must hit targets on the edges of the screen with their arms in time to the music. There will sometimes be stars that require players to follow it from one position to the other. There are also freestyle segments in which players earn points by freely moving about on screen.
There are 28 songs from several different artists including The Cheeky Girls, Daniel Bedingfield, Mis-Teeq, Earth, Wind & Fire, Elvis Presley, Fatboy Slim, Groove Armada, Good Charlotte, The Jackson 5, Jessica Simpson, Las Ketchup, Madonna, and Village People.
Source: Wikipedia, "EyeToy: Groove", available under the CC-BY-SA License.