PSP Vault has written an incredible article about the upcoming GPS accessory for the PSP. The 6000 Yen device will come out in December, and feature the following specs:

Reception Frequency: 1575.42MHz (L1 ban, C/A code)
Reception System: 20 Channel
Reception Sensitivity: Following: -153dBm
Captured: -140dBm
Position Renew Interval: ~1 second
Initial Position Acquisition Time: ~40 seconds
Positioning Precision: 5m (2DRAMS, -130dBm)
External Dimensions: 45 x 41 x 17mm (W x H x D)
Weight: 16g

As you can see from the specifications, the device takes 40 seconds to initially locate your position, but will recalculate your position every second after that. It has some pretty impressive precision, meaning it'll know your precise location, give or take 5 meters. While Sony hasn't officially revealed what the navigation system will look like, the Vault has unearthed a few interesting tidbits. The software is in development at Edia, a company that's developed impressive GPS software in the past. Their "Pontus" line of products have offered voice commands, route searches, automatic scrolling/rotation of maps, and even multimedia functionality. Hopefully, Sony and Edia won't fail to recognize the great potential for synergy between the PSP's native multimedia support and the GPS software.