I have an N97, and the SMS internal reader using TTS works very nice.
The APP shuold read also using the same TTS.
Also the APP can be changed be a Braille Writer, dividing the entire screen in 6 big dots. Will be better if each user can configure with the help of a people who can see and train to use the application.
This should help more the visually imparied.
I'm a teacher and last semester some of my studants implemented an SMS Braille Writer using the standard phone keyboard and worked very nice.
The use of TTS and the big screen of new touch phones can make the APP more useful for blind and visualy impaired people.