I've been thinking about this a lot, since I saw this video link text in fact. As far as I can tell, there's nothing going on with the strings -- he's muting them with his left hand -- which means the rest of the guitar is just a large object getting in the way.
So I was thinking about taking a super hot pickup and wiring it up to a piece of wood just large enough to hold the pickup, a volume pot, and a jack, and attaching some sort of clamp to the wood to allow me to clamp it to a mic stand, and to make positioning easier. Also, where the guitar's bridge would normally be grounded, I'd connect it to an alligator clamp (this would allow me to use the pickup on a tension cable or cymbal as though the cable were a huge guitar string).
I was wondering if any of you have ever done something like this... used a pickup, sans guitar, as a microphone for sound design.