A hacker called "AhMan" has created a software mod that enables two PSP
s to play PSOne games over an adhoc WiFi connection, although apparently this software is in early development -- really, when isn't this kind of hack
? For now the evidence is a YouTube video showing a pair of PSPs playing synchronized two player PSOne games, so we'll have to give them to benefit of the doubt that it's actually legit. If it is, you should be able to procure the software required within a reasonable amount of time: if you're willing, of course, to jump through the usual series of firmware
related hoops to get there.