I know some predatory starfish, some predatory crabs, and some predatory birds will eat keyhole limpets (which are different than true limpets which don't have a hole at the top of their shell) - none of these are reef-safe.
Some predatory snails (such as Murex/Muricid snails) may potentially eat them as well, but I haven't been able to find any confirmation of that - these may eat other snails, clams, etc. in your tank as well though, so attempt with caution.