Do I have one? Well, kind of. I keep breaking/damaging them, usually by dropping, (although one did a kamikazee jump out of my bag, and the latest one got water damage when it was rained on.) and then have to get a replacement. I've no idea what any of them were called. I don't have much use for one; occasionally I phone Conway when he's late for something, (once we were at opposite ends of the same bus station) but for the most part I'm not bothered either way.
And having your phone numbers stored electronically is a bad idea - so far I've lost two irreplaceable numbers because of my phone breaking.