Shameless reposting of slashdotted article.
From the article, “Control and Communication in the Animal and the Machine” is a cockroach-controlled mobile robot system. The system uses a living Madagascan hissing cockroach atop a modified trackball to control the three-wheeled robot. Infrared sensors also provide navigation feedback to create a semi-intelligent system, with the cockroach as the CPU.”
Garnet Hertz: Control and Communication in the Animal and the Machine