I typically try to avoid peepin' at knobs but I have been known to glance over a urinal divider if I hear an unusually powerful stream. Curiosity aside, this is a doorknob that allows you to see what's on the other side. Which, SPOILER!: your brother masturbating.
Hideyuki Nakayama's "A Room in the Glass Globe," developed in conjunction with door handle manufacturer LEVER, shows you a reflection of what's going on in the room behind it, cast in a sort of strange, dreamlike haze.
I dig it. And all you have to do for privacy is put a sock over your end. Unless you're an exhibitionist, in which case you should probably take all your doors off the hinges and sell them back to Home Depot anyway. Except for the bathroom. I don't care how big a pervert you are, no bathroom should ever go doorless. That's disgusting.
One more picture after the jump.