After the news that China has decided to force manufacturers to standardise phone charging ports to the mini-USB format, it turns out that there's an even easier way to get the industry-wide feature you want implemented: just be the FBI. What cellphone manufacturers are reluctant to include in-among all the blurb about Bluetooth and high-speed data connectivity is that apparently every recent phone sold in the US has a built-in tracking device that, once activated remotely, can be set to keep the microphone powered on even when the phone itself is switched off.
The FBI used the technology in collecting evidence for the recent Genovese crime family trial, and it should be made clear that they can only do so with the relevant court order. Saying that, just how difficult is it to get a court order in our age of super-terror? The only way to circumnavigate the tracker is removing the battery, which then makes the phone rather useless. In fact, you'd be better off carrying a small child's shoe, which could at least be used for storing your keys.
I'd be very interested to find out whereabouts in the phone circuitry the tracking device is located, from a purely geeky point of view. Anybody fancy hacking open their KRZR and going looking?