While there may be one very obvious Sony gaming peripheral that's screaming out for a rumble feature, that hasn't stopped modders from looking at adding the functionality to other Sony gadgets. A modder by the handle of FOO-f00 has given the PSP a basic rumble feature through a bundle of wires and circuitry that somehow translates the speaker volume into a signal that a motor can use. FOO-f00 made it so it only activates once a high enough pitch is reached, but we'd imagine the result is far from a perfect rumble feature. Still, the project is very much a proof of concept: and an awesome concept at that.
[Via PSP Fanboy]