They're adapters that let you use a home cordless phone or standard wired home phones to make and receive calls on your cell phone. I don't like carrying my phone around the house with me. Using one of these devices, I'd plug the cordless base station into the adapter and then set my Hero down somewhere within Bluetooth range. Then I could use any of the cordless phones around the house to make and receive calls. I've heard of them but don't know anyone that's actually used one. Since they're priced from $120 to $250 I don't really want to take a chance on one without hearing from somebody that uses one.