GBalpha has developed the first serious touchscreen GPS navigation system for the Nintendo DS. It features a U-Blox 5 chip, 32MB of extended memory and Google Earth integration.
The downside, and it is a big one, is that the device will not be DSi compatible. Still, if you have no plans on upgrading this might be of some interest—although a release date and a price have not been announced. [ds-gps via Maxconsole]