Watching: I was leaving a female friend's place one night after some homework and drinking.  As I was leaving, I had to walk by her bedroom window.  Glanced out of the corner of my eye and saw her taking her shirt off.  Needless to say, I watched the rest of that show. 
Being watched: Fucked a girl doggy-style on my old apartment balcony once.  We had a rather large apartment complex about 50 yards away, facing directly at my balcony.  Not sure if anyone saw, but they would have had to be blind not to.