Xcode will annotate files that have uncommitted changes (when they're in some sort of CVS) in it's equivalent of the project manager view and that can be quite helpful.

I'm not aware of a similar feature in KDevelop. 

Open questions:
- complexity/cost of querying the vcs subsystem for outstanding changes per file
- complexity of adding an indicator in the projectmanager view
- adding an additional indicator in the editor open document tabs (additional icon, or just a text label like [M])

Is any of those susceptible (or known) to make it not worth the effort to look into implementing this kind of feature?

Maybe easier: an overall "has uncommitted changes" indicator (basically, `git status`) on the project toplevel node and a per-file equivalent in the editor tabs (= only for open files) would already be a welcome addition too.