I just took a course on how to use one: can you imagine throwing one of those pads over a nipple ring and zapping someone? What if it electricity flowed though the ring? Would it blow the nipple off or fry the damn thing? What if it were a female: would she ever lactate properly after getting jolted? What if you padded a belly ring and a nipple ring: what kind of circut is that?
I'm pretty sure that body piercings containing jewelry would be just as harmful as a belt buckle, metallic pins in bones, metal rivets in jeans, watch bands, necklaces, earrings, and fillings.
I don't have the right information in front of me, and I don't feel like finding it, but pretty much, go ahead and get your nipples pierced. You can get shocked just as easily as anyone else.