With the Playstation 3 Japan launch just 2 days away, Sony Computer Entertainment Japan (SCEJ) has updated the PS3 firmware to ver 1.10. The new version will allow tighter integration with the PSP. However for that you will need to upgrade the PSP firmware to ver 3.0 which will be released by end of November. With the updates you can use the PSP as a remote control of the PS3. SCEJ states that this is only the beginning and future updates will further expand the network and gaming functions between the two consoles.

As communication between the PS3 and PSP will be done using Wi-Fi, only the 60GB PS3 will be compatible as the 20GB version lacks Wi-Fi.
Via - Playstation (Japanese)