iPhone text to speech? (Kindle also of interest...)

So, a dear friend of mine if pretty severely dyslexic. He's managed to work around this pretty well, but it means he doesn't get much reading in, and when he has 1200 pages of work related documentation that he's supposed to read while flying halfway around the world... yeah, that's just not happening.

He's also a happy iPhone user.

I'm wondering what people's experience has been with text to speech aps on the iPhone. Also, I think I gather that the Kindle reader for iPhone doesn't support text to speech? Is that true? If you have another text to speech ap, can you use it with the kindle reader? (Even if you can't, just having text to speech email would be a huge thing for him - not to mention the people who try to contact him over email!)

Also, general comments about Kindle text to speech would be appreciated (yeah, I know about TTS being disabled for some books. Still.)