Cool, finally someone's doing it...
Can't believe how much they're squeezing into that tiny thing!
Two of the biggest problems I see with that sort of thing though, are the screen size and that some people don't like to "wear" things on them. The first one will be a very, very serious obstacle I think, because screen real estate is a HUGE usability factor for smartphones. And if that thing is aspiring to become, more or less, a replacement for your smartphone, it better be able to show me all those images with which Dr. Rob and Tesshu have been topic-polluting the TNT thread recently...

The second obstacle/reason, the necessity to wear it, is what I think it also going to be a major problem for acceptance of the Google Glass stuff. Aside from it screwing with your peripheral vision... I have a feeling it would drive me absolutely insane, if I had to wear it all the time. But show knows; humans adapt...
One of these days they'll come up with some type of an unfolding sectional screen where sections connect seamlessly, I just know they will. Something similar to those gadgets they had in the movie "The One" with Jet Lee.