A bio-tracker was a device used to analyse reactions. In 0 BBY, Imperial Admiral Conan Antonio Motti installed bio-trackers in the helmets of every Death Star gunner at the request of Grand Moff Wilhuff Tarkin. After the destruction of Alderaan, Tarkin requested to have the mission report reaction data of the operation and discovered through the bio-trackers' results that several gunners, including Chief Gunner Endo Frant, had hesitated before firing Alderaan. As a result, Tarkin decided to punish the gunners for their failure by shutting them in an airlock and jettisoning them into space.