Navit uses the vector data to begin with, so it's an easy feature to support. The problem with tile-based nav apps like Mappero is that they don't "know" anything about the map. It seems to me that one might as well just switch to an app that uses vector data rather than tack on a whole new nav app-within-an-app. Edit: My recent take on this: http://talk.maemo.org/showthread.php?t=57698