Here's a great app for the iPhone/iPod/iPad that lets people with speech impairment to communicate very easily and efficiently with others. It is called Assistive Chat, and the strong point of this app is predictive text. Once the user types a letter, Assistive Chat gives them a list of six words. They can either choose one of the six words or type the next letter to get more suggested words. Once the needed word appears in the list, the user simply selects it, and that word becomes a part of the sentence. Once the entire sentence has been typed, a "speech" button read it out loud.
The idea behind this app is to have a decent conversation without involving too many keystrokes because that can be somewhat time consuming, and tiring.
Watch the video to see a demo of Assistive Chat.
The creators of this app advice people with disabilities to use it on the iPad because of its bigger screen surface. It sells on the app store for $24.99.