In downtown Lausanne, Switzerland (in this plaza, if you're in the area: http://g.co/maps/tupbn), there's an outdoor washroom that's enclosed in that sort of glass. When you walk up to it, all the walls are clear. When you lock the door, the walls go opaque.

Not really sure how it works, to be honest...

Edit: This is the stuff: http://en.wikipedia.org/wiki/Smart_glass