The Logitech Cordless MediaBoard for PlayStation 3 is currently one of the only Sony-certified--and totally compatible--cordless keyboards for the PS3, but it's really not a true PS3 keyboard.
Sony-certified and fully compatible with the Sony PlayStation 3; the Logitech Cordless MediaBoard for PlayStation 3 has a slim profile; is easy to set up; and has a built-in mousepad; obviating the need to connect a mouse to your PS3.
It's somewhat pricey; and there are no PS3-centric buttons/shortcuts available on the keyboard.