Project Indigo was UNIT's first experimental teleportation device. It was reverse-engineered from captured Sontaran technology.
The first person to (successfully) field-test the prototype was Martha Jones. Prior to this, Jack Harkness warned Martha against using it given its experimental nature. As the device teleported her to her mother's house, "the place [she] most wanted to be", it suggested the integration of a neural interface device for determining destination in order to make the technology man-portable. Martha later used the device again, to teleport herself to the vicinity of the Osterhagen base in Germany, where it was last seen discarded by the door of the detonation control chamber. (TV: Journey's End)