Cool, are you actually controlling navit at all or just showing it?
I know some work has been done recently on being able to pass commands to Navit on Windows (CE at least) via window messages.
I've got it embedded on my own front end, but it is still really unstable on Windows. They don't seem to have any developers willing to take it on.
I haven't even get a response to my bug report to get rid of the console window it shows.
They are aware of the problem that it can't save it's bookmarks.txt file properly on Windows 7 due to UAC, but they don't seem to have the will to get it to write to the users folder instead of program files. (
http://trac.navit-project.org/ticket/996)