I currently use my PSP as a replacement monitor for a laptop with a shattered monitor, it uses a program called PSPdisp which works solely with windows and plugs in through the USB port.
How difficult would it be to get a similar program to work with linux?
From the FAQ of the creator's website:
"Will there be a version for Mac OS X / Linux / etc.?
Not from me. The download includes the complete source code, though. So if anyone wants to port PSPdisp, just go ahead. While all functions for acquiring the display contents and the GUI are platform specific to Windows, the data transmission is done using standard socket API and libusb, so they should be fairly portable."