A crew locator was a piece of sensor technology used on starships to indicate the location of crewmembers and other people that pass by them. Crew locators could not show where people went once they passed by them.

The USS Enterprise-D was equipped with crew locators, and in 2364, crew locators were used to indicate the location of feuding Antican and Selay delegates that were being transported by the ship. (TNG: "Lonely Among Us")