Glass does not have a light of any kind that comes on while it is recording. The closest you have is that the screen itself is visible from the front (due to how light refracts through a prism). I have heard that the older Glass units that were being demoed by Google employees did have such a light, but if that was true it was removed for the Explorer Edition units.
Oh. Wow, I'm quite surprised they'd remove that, seems like it would make them a bit easier for people to accept if there's a clear sign of whether they're recording. I expect not doing so is going to mean they're treated like holding your phone up, and there's quite a few places that's really not going to fly.
