That Japan only GPS add-on for the PSP doesn't look so Japan only anymore. Sony's CES page lists the GPS system, leading most to believe the peripheral, already out in Japan, will get a Western release. Here's how the Sony site describes it:
Explore the world with GPS on your PSP. Utlising the GPS peripheral and the latest mapping software on UMD, your PSP will provide 2D/3D locations, driving directions, POI's, and even downloadable city guides. With an easy search feature and customisable settings, GPS on PSP is the easiest way to navigate new areas and cities.