Let me start off by saying I love to masturbate, and I always fantasize about others watching me, but I usually don't have the guts to do it in public or anything like that.
One time last week, though, I tried to allow two women to watch. My first floor apartment has a huge window with a little portico in front of it. People occasionally stand out there to get some air since we don't have balconies in my building. Anyone can look into my apartment, so at night I close the blinds but during the day I let all the natural light in.
Anyway it was approaching dark, maybe 7pm but there was still plenty of light. There were two women on the portico talking, facing away from me out to the street. I was horny and realized I they might turn to look if I turned on a light inside. I couldn't tell whether they did, but I took off my clothes and began to stroke. I had an amazing orgasm with them right outside my window, but I still don't know whether they saw or not. I hope they'll 'catch' me in the future, and even that they'd tell me they want to watch me for real, from inside my apartment.