From Halopedia, the Halo wiki
The SRT Universal Global Positioning System Device is a Universal Global Positioning System device, compatible with the armor accessory Tactical/UGPS wrist dock.
The SRT is a terminal that can be docked into the Tactical/UGPS wrist dock.
The SRT was used by Jun-A266 at the tail end of the Human-Covenant War.
The SRT was also used by Owen-B096 around the Battle of Meridian, he was also using one at Outpost Discovery.