These sci-fi glasses are looking to keep the wearer safe, no matter what the circumstance is. These glasses will shield the wearer from whatever things happen to freak them out by shading up whenever danger approaches.
In the Hitchhiker's Guide to the Galaxy series, there was a pair of glasses that would darken whenever there was danger around. Whenever there was serious peril, the glasses would go completely black. These glasses seemed like a piece of fiction, but for a contest, a member of Hack a Day made them into a reality.
There should be a disclaimer on the glasses, as just because they darken, doesn't mean that the danger goes away. In fact, it could be especially dangerous because it somewhat blocks the user's vision.