I'm usually not a fan of buying 3rd party peripherals of any sort but this is pretty bad ass..however i think the biggest problem is going to be with the screen size..its too damn small for a tool like this... Also not sure if this would work for standard FPS.. or the silentscope type games where your gun is your sight... meaning you can only see whats directly in front of you...

Check it out Here..

To bad i dont own any FPS's...nore do any FPS games look enticing on the PSP...not to mention they said they idea is practically scrapped.