All basic features for
- importing OSM data
- quering the resulting database
- rendering fancy maps nobody have ever seen
- finding locations no one else could find
- and routing you to all these strange places
You should be able to implement your application with all basic features required for a navigation application. However there are still corners, we have not yet visited, some ideas though of but not implemented yet. The following list of documents should give you an overview what is already there - and what is not.