Outside window covering

[Andrew Faukner]

I have a duplex with a bathroom window on a side street, and the other on an alley. They are over the tub/shower. I would like to have something on the outside of the window that would block the view of someone showering, yet they would be able to have the window open. Can you think of somehow to accomplish this? 

[Theresa Harris]

What about frosting the window?