Our daily carry devices are amazing -- they can download all kinds of useful information, such as top secret communications and maps -- very useful for a spy! However, they can also upload important data -- including our precise whereabouts at any given time!
Even when you're not using your phone, there's always the chance that you're leaving electronic breadcrumbs about your location. This kind of data is exchanged between cell phone towers as you move about. If you want to be certain you're in full stealth mode, you may need to seal up your phone from all incoming and outgoing radio waves!
A Faraday cage does exactly that, and the best part is that it's very easy to make. All you need is some conductive wire mesh fabric and a way to close it up so that no radio waves can get in or out.
I've made a custom pouch for my phone using a sewing machine. shown here. As soon as I drop it in the pouch, it goes into a radio wave black hole.
Everything from cell reception to WiFi, from Bluetooth to GPS are immediately snuffed out as long as the phone is tightly sealed up in the bag!
WiFi and Bluetooth will usually reconnect quickly as you open the pouch, cell service can take a bit longer.
To make your own RF pouch, check out this learn guide!