As someone who intends to use Glass or something like it for GPS while driving, I really don't see that Glass will be any more distracting than having my tablet do GPS for me, or my phone, or a dedicated GPS on the dash. I recognize that it may be slightly more distracting than the dedicated GPS due to the possibility of notifications suddenly taking focus on the screen, but no more so than when the same thing happens on my phone when I'm using it for GPS.
I understand the concern about people playing on the internet, or actually watching movies on it, but should the device's usage be outlawed due to things that it is simply capable of doing?
I recognize that these aren't exactly HUDs, but HUDs have been proven to not significantly increase reaction times, and to decrease the amount of time with your eyes off-road. From every review I've read about Glass online, the display is out of the way unless you want to look at it, and easily ignored when you're focused on something else.
Maybe I'm giving other drivers too much credit. Most people probably will be facebooking on them, not simply using them as a convenient display for GPS guidance.