That's already possible. With a program like e-triloquist on a smaller laptop, you can voice things through typing. On the PDA front, you can download a screen-reader meant for the blind, set it to echo (speak) the words you type, and type in notepad.
That said, a deaf person who can speak is a deaf person who doesn't always need such technology, and in most cases, doesn't need it at all. There's no way to make a deaf accent really go away, although with some people, it's more profound than others. But it's nothing to be ashamed about or try to mask.
