NSA whistleblower Edward Snowden has teamed up with renowned hardware hacker Andrew “Bunnie” Huang on the development of an iPhone accessory designed to detect when the phone’s radios are actively transmitting.

The idea behind the device is to provide reporters and journalists traveling in dangerous regions with a way to determine if their iPhone is being tracked or otherwise giving up its location.

Certain governments, they claim, have access to high-level hacking techniques and can even deploy malware that can trick people into thinking their device is off when it’s really awake and actively eavesdropping on conversations.

The accessory, which is designed to look somewhat like a standard phone case, will feature a mono-color screen and function like an oscilloscope by routing tiny wires into the iPhone through the SIM card slot (the SIM card would be moved and housed inside the accessory) and attaching to test points on the phone’s circuit board.

The wires would be capable of reading electrical signals from the phone’s antennas and warn the user if radios are transmitting when they shouldn’t be. Huang tells Wired that their device may even include a kill switch that would turn the handset off automatically.

Dubbed an introspection engine, the device is little more than a concept at this point. The duo say they’ll lean on Chinese manufacturers to build it and that both the software and hardware will be fully open-source to curb any potential tinkering by its manufacturers.