Communication between a Deaf person and a hearing person is a two-way street, and this tool really only addresses one of those streets.
The tool transcribes the audible speech of the hearing person, allowing the Deaf person to read the transcription.
But if the Deaf person wants to sign a response, they're out of luck. Instead, they need to type their response on the device.
That's OK, but in a "this'll make do in a pinch" kind of way. The ideal is that both the Deaf person and the Hearing person are able to communicate without typing.
There is some pretty cool research around signing-to-text translation -- Matt Huenerfauth https://huenerfauth.ist.rit.edu is doing some really interesting stuff, for example -- but as far as I know it's not ready for prime time.