I don't understand why it needs to have a camera on it. I just want a heads up display. It requires a smartphone right? Are there ANY smartphones which do not already have a camera on it?
If I'm walking along reading a text on a glass display and I see Bigfoot, I could pull out my phone and use that camera. Not having a camera on the glass itself would not be an issue. Bigfoot could say "Hey man, could you not film me," and I could put my phone back in my pocket and apologize. Then bigfoot would say "Are you still filming me with that google glass?" and I could say "No, it's glass 2, so there's no camera" and he would say "Oh cool, now I know I'm not being filmed and I can relax. Hey, have you seen 'Harry and the Hendersons.'" And I could say "Uh... I'm watching it right now!"
With the camera on there, I would assure him I'm not filming him still, and he'd still be nervous, and then might rip my head off. That's why I won't be buying a glass with a camera on it. I like my head where it is.