The Atari Mindlink, which (luckily) never did end up getting released, apparently worked primarily by reading your eyebrow muscles. I guess Eyebrow-Link didn't sound whizzy enough. Maybe it could have been the FrownMaster. Or the ForeheadTronic.
Take a quick look at it [link|http://www.atarihq.com/museum/2678/mindlink.html|here].