Communication on Shabbat

I'm a conservative Jew and am an occupational therapist. Recently on a forum I'm in for OT's, someone asked a question regarding Shabbat and augmentive communication. Basically, if someone uses a technological device to speak for themselves (think Stephen Hawking eye gaze device) what would be the rules related to Shabbat? I would assume they would not be able to use it during Shabbat? Seems limiting and the only solution I could think of is a picture board they could use with their hand (it their hands were functional), and if anyone knows ways around this, I would love to pick your brain a bit.

Shabbat shalom!