The news that Apple has filed a patent application on a technology for tethering rechargeable devices (like iPods) to particular chargers caused a perceptible rise in this blogger’s blood pressure. The idea is that the device will only allow its batteries to be recharged if it is connected to an authorized charger. But Ed Felten has some characteristically measured thoughts about the idea — for example it’s utility as an anti-theft measure — so I’ve calmed down.