I was pointed to this article that talks about using AIM for conversations between hearing-imparied and non-hearing imparied individuals. This allows the two parties to communicate without the use of TTY terminal.
Still, there is a call center transcribing the information. This seems like a really interesting application for speech recognition. Assuming accuracy was high enough, this would remove the potential awkardness of speaking while there was a transcriber present. I know there are other things to consider here, but to me, the link seems obvious.