It's called "Rapex"
www.snopes.com/photos/crime/rapex.asp
I think it's a really bad idea and am struggling to articulate properly WHY.
It doesn't stop the actual rape.
It might be a fairy story anyway.
It won't work unless you walk around with a condom up your innards 24/7.
Victim blaming and smacks of "why did you wear a short skirt" = "why didn't you have a rapex in"