With some conductive fabric and spirit gum, you can make a simple binary switch that attaches to your eyelids. Andrew Schneider used some of these to make a polaroid camera that takes a snapshot when you blink.
When I first saw these, I was reminded of cyborgs in television and film and how they typically exhibit facial twitches when receiving data or jacking in to the network brain. I always thought the apparent “glitch” was sort of a stupid film device, but mabe it’s not that far from the future truth. Left wink, change music track. Right wink, shoot photo with the camera tilak in your forehead. Triple-blink, stimulate adrenal gland to release epinephrine. Eyes closed for one minute, dose of melatonin.
Experimental Device for Performance: Eyelash Switch – Link