Well. I'm going to Berkeley now. And I have absolutely no time to code... I haven't been on mp3car for over a month. So... here's the source to NaviVoice. I hope someone can give it the love and care that it deserves.
It will need some fine tuning, and probably replacement of a few components (i.e. menu on the left).
The code is given under the condition that you keep the code open source and give update to the community.