of lmilitary tech: tooth mics. C_A , IN-Q-TEL, Sonitus

im sure they're beyond this now since they are letting us know.

"The Molar Mic connects to its transmitter via near-field magnetic induction. It’s similar to Bluetooth, encryptable, but more difficult to detect and able to pass through water."

"Sonitus received early funding from In-Q-Tel, the nonprofit investment arm of the CIA"

https://www.defenseone.com/technology/2018/09/military-now-has-tooth-mics-invisible-hands-free-radio-calls/151145/