I really don't know, but I would assume that, as the device could only be removed by a doctor, that would serve to reduce the number of women who might use it as a form of revenge or to harm someone.
The assumption is that the device causes so much pain that it incapacitates the attacker. In the instance of gang rape (very common in SA) it would surely leave the women open to further violence from the other attackers. But she would have been a victim of that anyway.
I cannot say I am for it, but I am not really against it either. The level of violence is truly shocking and I cannot help but think any weapon women have to protect themselves has got to be a good thing. Especially when rape in SA (and other African countries) often results in a death sentence for the victim, given the likelihood of the transmission of HIV, and the cultural belief that raping a virgin will cure you of AIDS.