SmartGuide?

Oral-B's Triumph SmartGuide toothbrush, available in the United Kingdom for the equivalent of about $280, uses navigation technology to transmit the exact location of the toothbrush to a base unit so that the user can see which areas in his mouth the brush might have missed. The wireless LCD mouth display can be mounted on a mirror or held in the free hand. [Daily Telegraph (London), 8-31-07]

Yep, we wouldn't want to take a chance of going over the same space TWICE with an old fashion manual toothbrush. Thank you, technology.