Can the 'Directions' be made to function like on my pc laptop, where you can drag-and-drop points on the initial route in order to generate an alternate route?
As for the weather radar layering, Google Earth has that option. I don't know if that's compatible with what you've done with this project. But I will say this about the Google Earth radar layer that I used on my laptop: I didn't like that it was solidly superimposed over the map. For the purpose of integrating with navigation, I think radar imaging would be more of a hinderance if it's not available as a translucent layer. Again, great application so far.