Squids (Superconducting Quantum Inference Detectors) are supersensitive detectors of magnetic fields. Even the primitive models could measure a field a billionth the strength of geomagnetic force. They were used in the War to find submarines, suss out enemy cyber systems. Jones had squid sensors to sweep enemy mines in the Pacific. They are used in decryption.
Although cops are equipped with parabolic microphones and lasers that can pull a whisper out of cheering stadium, no government let them have Squids, to avoid interdepartmental funnies and Watergate scandals.
Data carriers like Johnny knew about Squids who could dig out a password from their brain chip, but don't mention them to their clients.
The use of SQUIDS as a military application in anti-submarine warfare, is only a potential proposal as of now.