XLink Kai is a tunneling software that allows players to connect their Ad-Hoc only PSP games (which required the two players to be in proximity with each other) and lets you play them against anybody in the world. I just found about it myself and I've finally got it up and running. In terms of hardware, all you need is a PSP (obviously), a PC and a wireless router. The only software you need is the XLink Kai program and a registration with the site, both of which are absolutely free. Here is the link to the main site for those interested:
i got a psp, and i got wipeout, mga, mlb, and untold egends.
i need to get xlink workng, but i cant play any psp gmes other then mga. i only have 1 arm from my surgery to my right shoulder, sooooo i cant play geams right now lol.