Basic TTS service speaking all/most text displayed

[Per]

Hi all,
I'm a new member of this group with a recently aquired android phone
(Galaxy S). I'm visually impaired and therefore dependent on TTS on my
computer (using Jaws) and on my phone.
I have a background in s/w design and coding on apps level but I have
tried and succeeded on a slightly deeper level developing a
softkeyboard for android which speaks the key input while typing and
the complete input when done.
Now I'm pursuing the next challenge - to get android to speek
all(most) text displayed on the screen, e.g. dialog text, lists, icon
text etc. I have the building blocks for developing a speaking
application and I can find several such apps on the Market. However,
the challenge is to get android to speak text for all/most
applications - also the ones not designed specifically to speak. In
Windows, this is done by intercepting text on display driver level,
but I have not been able to find the necessary basic features in
android (I have no experience with developing drivers etc).
Is there anyone out there who can help in this area? I'm interested in
development myself but is also interested in helping with good ideas
and testing if there is anyone out there who has already started in
this direction.

Looking forward to some good ideas/cooperation
Per