I’ve heard of these.

With a cell phone, a computer, a few dollars’ worth of parts and some technical savvy, the individual tinkerer can indeed construct a device that will track another cell phone, [said a COMINT consultant,] a former communications engineer with the Defense Intelligence Agency, [who] described encounters with cellular intercept systems “that were literally a telephone…turned it into what’s called a ‘vampire’…..Every time the target’s phone would ring or he’d use his phone, it would automatically lock onto it and start a recorder going. And [the engineers] were just using a phone [with] about $50 worth of extra circuitry on it, and it’s a piece of cake.”

http://www.inet-one.com/cypherpunks/dir.1998.06.22-1998.06.28/msg00100.html

In other words, a cheap phone tap, perhaps even mobile. I would imagine a vampire-buster would work on similar principles as a vampire itself. A savvy tapper would want to disable any broadcast capability on his vampire, though.

Oh! Damn, I thought he was onto something for a moment there. Here’s the real deal.

Mr. Bush spent most of his speech talking about “vampire” appliances, such as cell-phone chargers and computers that consume electricity even when the phones are fully charged and the computers are idle. He deputized Energy Secretary Spencer Abraham as “the new vampire slayer” who will promote devices that use a fraction of the electricity.

“While that may not be much of a savings on an individual unit basis, when you multiply the amount of chargers plugged into people’s walls all across America, one can begin to realize significant energy savings,” the president said.

“We’re talking about 52 billion kilowatt-hours of power a year, or the equivalent of 26 average-sized power plants,” he added.

http://www.google.com/search?q=cache:uOPkkT90FpM:www.washtimes.com/national/20010629-30711831.htm

There’s a point here. For instance, most people have no idea that their television is drawing power 24 hours a day, even when it’s turned off. This is the “instant-on” feature that allows the tube to flash on without warming up first as on older sets. But it needs to draw a few watts — as many as 10 — to do it. Multiply that across a metropolitan area …