As a creative-writer-type who also dabbles in code, I've found
org-mode extremely useful to not only to organize notes relating to
a project but also for creative writing. Structure and
navigation/linking is a breeze and export is well developed.
I've come across http://www.emacswiki.org/emacs/SentenceHighlight
lately and tried it with org instead of the outline mode it was
written for and it seems to work very well. I find it a very useful
aid.
It might be worth polling people to see if there's enough interest
for this kind of feature and including it if the reaction's positive
as it's a fairly trivial piece of code.
It also occurred to me that for someone who knows what they're doing
(not me!) it should be trivial to adapt it to function in code
blocks to higlight the current bracketed expression or function ...
just an idea.