only a few weeks ago an app for Android devices has been published called ZANavi.
some outstanding features may be:
realtime vector rendereing of OSM data -> no download of tiles needed.
map data can be downloaded over the air or via PC to store it offline on your phone.
Quite nice routing engine that can process turn restrictions.
No dealing with parameter file navit.xml
So all android users who are looking for a navigation app can try this, find bugs in ZANAvi or even core Navit, and find out the difference between them.