You know, it took me a while to figure it out. But, to be honest, I don't think it would work; just pissing off the man and pushing the device far enough in to injure the woman.
Femdefence is an on-going project first presented in 2003. The project includes the creation of an imaginary product, which bears the project’s name. The “product“ is a kind of protection against rape, somewhat similar to a tampon in that it’s user carries it inserted into her vagina. The basic idea is that the woman carries the protective device in her vagina. In it there is a sharp pin which has a penetrating effect on the perpetrator’s penis in the event of a rape. The construction is such that the pin still cannot injure the bearer. The design of the design is based on a similar construction invented by a Swedish woman named Anita Ingmarsdotter. She came to work on her invention after a series of rape cases in Sweden that received a lot of public attention.
I have two thoughts on this just off the top of my head:
1) What keeps a rapist from removing this device with the handy string?
2) What is the risk of injury to the woman wearing it?
3) (I thought I only had two?) Will there be a version for men?
Before you scoff at #3, I bet that there are tons more rapes of men in prison than there are of women on the outside. But i have nothing to back that up . . .
All in all, I'd have to say that I like it. However, I think they need to actually start making these for the "discussion" to continue.