Great post. Its one of those things many people know but we often forget about. I'd guess most people don't know this though so it is a good reminder.

Another tip. You can acquire a faraday bag/box and be even more sure your device is not communicating with anything. I recommend testing it by trying to call the phone. Trying to use other things like wifi and bluetooth. If you control a wifi network you can see if the device drops off the network for example.

Now that you have tested the faraday enclosure you can use this as an added layer of privacy/control.