I discover osmbonuspack but the API information and the documentation in the wiki is very low.
http://code.google.com/p/osmbonuspack/
I think that this library is very interesting to upgrade osmdroid but I can not learn to use it.
Has been used by someone?
You can have a look again in the wiki, I just completed with a tutorial, here:
http://code.google.com/p/osmbonuspack/wiki/Tutorial_1
Hope it will help!
To go further, there is also a sample application in the source repository: OSMBonusPackDemo, and the javadoc. And don't hesitate to ask questions in the issues of the project.