Theres this trendy little bar/lounge in philadelphia's old city section called paradigm which has these unisex bathrooms with doors that are clear when unlocked and fog up as soon as you lock them[1]. Once in a while it makes for a usually not quite desirable show when some one(or two) is drunk enough to shut the door without locking it and not notice the opacity.
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.
[1] http://s3-media3.ak.yelpcdn.com/bphoto/I7ICPsQ45YVbLzKEBiHND... left locked, right unlocked