NAV marker transmitter
From Halopedia, the Halo wiki
They are small devices, relatively the size of a tick, and can be discreetly attached to an object. The transmitter will then broadcast the location of that object to a nearby UNSC heads-up display calibrated to their frequency.
List of appearances
- Halo: The Fall of Reach, page 80
- Halo: First Strike, page 13