When was the last time you winked? When was the last time you winked and didn't immediately regret it? It's probably been a while, but Google is aiming making winking cool again(?), by hard-coding some ;) functionality right into Glass.
The code was dug up by Redditor fodawim, who found some variables with variations on the name EYE_GESTURE_WINK. Wink functionality can be turned off and on it seems, and would have to be calibrated to work. The code has an explicit reference to "wink to take a picture" feature, but it'd make sense if you could us it for just about anything.
Glass already has a sensor on the inside that's used to detect whether or not it's currently on a head, and the thought is that this same sensor could be used to watch your eye with a little extra calibration. Of course, since it's just watching the one eye, the winks are bound to have to be exaggerated affairs so the sensor can be sure it's not just catching one half of a standard blink.
So if the idea of standing around, staring off into the distance, rubbing the edge of your glasses and talking to yourself wasn't appealing enough, you can add a dash of prnounced winking to the mix as well. "No, no. Don't worry. I'm not recording." ;) [Google Glass Apps]