TTY devices

TTY devices Hello, I was wondering if anyone has experience with TTY devices. They are used as a way to "talk" on the phone for people with hearing and speech disabilities. I have tried looking into getting one, but I have no idea where to start. I want to use it with my iphone, and I know there is an extra adapter I have to buy. They all seem to look big and clunky, and that's not really what I want. I am surprised there is just not an app that does this. Any help would be appreciated