This would be rather annoying for me as I cannot wink with my right eye (only my left, apparently not uncommon[0]). I suppose blinking would do the trick though.
If the sensor is only on the right side I guess it won't be able to detect actions from the left eye.
My first thought is with timing or counting winks. "Three fast winks" = "Take Picture".
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[ 5.0 ms ] story [ 23.0 ms ] thread[0]: http://en.wikipedia.org/wiki/Wink#Physiological_ability