We already saw that there is a GPS for the game boy.The Feature details the possibilities.

Using the inexpensive GameBoy as a platform for non-entertainment applications is a brilliant approach to launch more wireless devices. Perhaps something like PacManhattan could arise from GPS-enabled GameBoys. RedSky is hip to this idea -- they've developed some open APIs for game developers to use the RedSky hardware for their own applications. The device can hold 8 megabtyes of pictures and maps that users can download from their PCs. Maybe in the future people will be downloading GameBoy geo-games? (...) Eric Johnson, their CTO, envisions GameBoy-readable maps of California up at the cash register at a local gas station. His eyes lit up as he described the incredible power of the GBA/GPS combination. Most GPS devices just show you latitude and longitude he points out, but this device presents a color location map, with value-added services like mentioning the nearest restaurant. This geographical spin will be available for a relatively cheap price. "We're going to bring mobile maps to the masses," he said, with a believer's expression on his face.