With GPS standard in most Japanese cars and many cell phones, Sony's move to create a GPS receiver for the PSP was surprising. Blog HiroIro has a fine product review using Japanese UMD title MAPLUS.
Comparisons are drawn between a Panasonic car navigational system of the PSP with the Panasonic navi starting up as soon as the engine turns over while the PSP takes the requisite five minutes to get fired up. The Panasonic navi can make it through tunnels or underground, no problemo while the PSP croaks. Pulling up addresses, names and phone numbers are easy on the Panasonic system; the PSP only provides addresses, which are "difficult on the eyes" to read.
Verdict? Standard car navi wins.
Motorcycles don't really have navigational systems (none that I am aware off). So the PSP navi might actually be of some use. Here's the set-up, above. The portable is slipped in a map case designed for touring. An external battery beefs up the portable's life. Earphones make it possible directions given from the software as during the day, seeing the PSP screen is difficult. Night is much easier.
Problems: It's impossible to tell the difference between national roads and prefectural ones, and HiroIro says the software's still seems like it was created 10 years ago. Now that's an endorsement.