This has been around for a while. Also, it's less than ideal, as it is simply a cache of the map (meaning no directions). Its good if you need a traditional map map, but not so good if you're used to the robustness of having a smartphone map.
I used it while abroad. Since the GPS works, you can see where you are on the map, which is a big plus over only a paper map. Obviously getting data access would be even better, but it's a nice free alternative.