What tablet and software for a partially sighted person?

RobHart writes: My friend has had both retinas detach, twice. He is legally blind but partially sighted. He has a number of devices that help him read (either by magnifying the text or as text to speech) — but none are really portable. What do Slash Dotters recommend (if anything) in terms of a tablet and software that will make it possible for him to do email and read at least some web sites?