You know they have to have a website. If 2 or more people get together and have an idea, they have to create a website.
http://www.purityrings.com/
and you know wiki has it covered:
http://en.wikipedia.org/wiki/Purity_ring
You can probably find some Purity Balls on YouTube. That is creeeeepy.
On the subject of the Rings, wouldn't a Chastity Belt work better?