Animal Controlled Computer Games is the graduation project from Wim van Eck, a study college and friend of mine. In his project he build a Pacman game, in that the player can play Pacman against real crickets, that controls the ghosts in the Pacman maze. By doing this he analyzes the advantages and disadvantages of real-time behaviour of live animals in comparison to behavior-generating code in computer games.
Interesting about this idea in my opinion is, that through the use of real life elements in a game, the game gets unpredictable. It happens once to him that during playing the game one cricket piled his skin. Because of the new and white skin of the cricket, the color detecting system of the game could not detect the cricket for certain period. During this period the cricket was a real ghost for the system.
More information can be found at Wim’s site or at the mediatechnology site (projects > Animal Controlled Computer Games).