For a best experience, use Google TTS Speech engine.

The app transforms your tablet or smartphone into a communicator.
Useful for those who have difficulty using language as a communication channel.
The app is useful in case of congenital disabilities, acquired and/or temporary, allowing through the speech of the device on which it is installed, a fast voice prompt, communicating effectively problems, needs and requests.

A communicator useful also for those people who have had their vocal chords removed and for hospitalized inpatients who are unable to speak the english language.

Available a simple mode for severe disability.

One of the 2013 best app: Productivity - for the Christopher & Dana Reeve Foundation.