While it takes practice to learn how to make these things work with one's body, they are amazing little devices, capable of producing extraordinary pleasure by stimulating "peristaltic" orgasms.
The Peridise, from the fine folks at Aneros, is meant to be used anally, much like their other toys. These ones however, are advertised as being for anyone: for people without prostates, as well as for people with prostates. As it happens, I do have a prostate, so my experience is reported from that point of view.