This also detects when the GPS is used. If the phone has GPS and cell radio (for reception and transmission) disabled, it's a lot harder for any malware to figure out its location (not impossible -- there is some research about identifying locations in a metro network using an accelerometer alone).

While it's easy to prevent the phone from recording your conversation (just place it somewhere out of earshot, maybe next to a noise source for the duration of the conversation alone), it's much harder to prevent it from learning where you're going (if you're taking it with you).