I've finally found a few minutes to install this, and...Wow, it really does show great potential. Going forward from here;

1) Jan, are you looking to integrating this into gpsapp more tightly (possible non-US ramifications), or perhaps reworking gpsapp to allow a 'modular' moving map 'plug-in' (allowing other potential data sources to be used if they come along). Or are you intending for roadmapgpsapp to remain a derivative of gpsapp?

2) Assuming for the moment that the zoom scales can be unified, we still have some UI hurdles to jump;
a) gpsapp currently displays a dim route with bright waypoints. The roadmap lines are always bright. This is almost the inverse of what is ideal. Obviously with only 3 shades and black available we are very limited in how to resolve this. Ideally major highways would be brighter than back roads. But how do we then indicate the route over the top? Perhaps a dotted line that inverts itself a few times/second? Perhaps an animated line that color-cycles through the 4 shades...Hmm. picture/thousand words;


b) It would be nice if we could have a larger virtual screen, and then a pan mode. This way we could look around at a higher resolution.
c) It'd be cool to pop up the nearest road name. Chances are that we should be on it.
d) Labelling major highways at an appropriate resolution.
e) De-cluttering some of the big-scale zooms. It appears as if we still get dots where some of the roads were. Ideally if I go to a 5mile+ scale, all I want to see are major roads. (Interstates, turnpikes etc)
f) It'd be nice to shade-fill water. It appears as though it is displaying line data for shorelines already. I'm not sure how feasible this is.
g) Remove transparency from gpsapp popup route directions.

3) It would be cool to implement a road name search. My brief source code excusion suggests that the underlying data should be there in a searchable form. I don't know if it would be possible to implement a fuzzy search similar to the empeg's song search feature, but that would be ideal. I'm guessing that the database would be too large to keep in memory, and the fuzzy search would require looking in multiple parts of the database simultaneously until the search gets narrowed down. But I can dream
...and then highlight/mark the resulting road whenever it appears in our viewport. (and ensure that it appears in large scale zoom modes too)

Lots of other exciting potential...