It is the distraction to driving that illegal. All forms of distracted driving are illegal, at least that is my understanding of the law in Colorado and Texas USA. So purposely taking 2 second blinks, driving with one of two good eyes closed, driving with your knees, etc is a ticketable offense. Driving while holding a phone to your ear would fall into this category. Wearing google glass while off does not seem to.

Additional laws exist probably to increase the fine or the ease of enforcement of various distractions like using a phone.