The Hollow Tongue Relay is a passive dead-drop infrastructure device disguised as an ordinary piece of urban furniture or commercial detritus — a cracked utility panel, a branded vending machine fascia, a municipal drainage marker. Internally it houses a heavily shielded, ultra-low-power mesh node that stores encrypted message packets in a write-once buffer, broadcasting nothing until a specifically keyed query device passes within two meters and triggers a silent, microsecond burst transmission. The relay never initiates contact and emits no continuous signal, making it invisible to both passive monitoring grids and active sweep protocols.