Devices emit radiation whether they are using the radio or not. If its burning power, there is an emission, albeit small in comparison and probably hard to dete

Devices emit radiation whether they are using the radio or not. If its burning power, there is an emission, albeit small in comparison and probably hard to detect without specialized instruments. If the radios are simply on, link layer protocols will be transmitting control signals that can easily be detected with something as simple as a smart phone.