it could potentialy work, the main issue is decoding the information, I use a logitech wireless keyboard, and it uses RF (radio frequency) modulation, not WiFi, and not IRDA, and for the time being, it would be impossible to pick up the signal from a PSP, however, there is an option of data transfer from a PC with a keyboard to the PSP, it shouldnt be hard to program software to transfer information from a PC to a PSP via Wireless..
the onnly thing would be, you'd need a seperate wireless network for PC to psp Infrastructure data transfer, however in a sence it should be possible to transfer whats typed on PC to PSP...