We already have the Sony Remote by melman101 to use on Sony electronics, but recent news shows that the PSP is planned to also be used as a wireless controller for the PS3:
“However, you will be able to use your PSP's WiFi capability to play movies and flick through all of the files and folders on your PS3 from the comfort of your sofa. And since the two machines will also share Memory Stick Duo cards, you will be able to transfer photos and films between the devices.”
The article describes that the PSP will be using its WiFi capabilities to connect to the PS3, which to me seems odd, but only time will tell. I for one hope that it will use the Infrared port, allowing for developers to further expand on this largely untouched aspect of homebrew.
You can read the full article [here].
maybe its just me, but it seems that wifi would be a rather expensive option to equip in all of the ps3's controllers. maybe the price of this has been dropping, but IrDA would seem the way to go (except for the line of sight factor). hmmmmmm