Only in Japan you will find researchers that build gadgets like the Wink Glasses: the clip-on device monitors your alertness by counting how often you blink. If it senses that you are dozing out (your blink frequency decreases), the glass will become opaque – and apparently, that wakes one up. Not that it won’t work if you’re completely asleep, obviously.
It makes sense, I guess. If my optic nerve says “I’m blind, I’m blind!” all the sudden, I bet that the rest of the brain is going to take notice and try to figure out what’s going on. You might even have primal reflexes like pumping adrenaline and things like that that kick-in.