I use good old Ivory Soap as a leg cramp remedy. It works. I don't how how, but as Pippinwhite noted, it's surely not going to hurt you.
I'd recommend using regular soap, though, not a glycerine soap like Pears. That's good soap, but the glycerine base would probably get really sticky over time, and I don't know if it would work as well. Ivory Soap is cheap and if it doesn't work, you haven't lost anything. Just put it in the soap dish in the bathroom and use it for its intended purpose. No problem.