This iPhone project shows a basic usage of the route-me mapping library, along with its built-in support for offline-capable MBTiles map tiles, together with some custom additions that allow contextual data to be embedded along with the tiles on a per-pixel basis in a space-efficient way. When you touch a country, you get its name and an image of its flag, for the entire world, at six zoom levels, for every pixel on the globe, in a 29MB data file.
More info on creating the interactivity features at:
http://developmentseed.org/blog/2011/may/16/tilemill-020-release
Screenshot of the app:
