Project Indigo

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. 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).

Conjecture
The Dalek massacre of UNIT personnel around the globe likely resulted in the deaths of Project Indigo's design teams and provided private commercial interests with the window of opportunity to steal the contents of the organisation's extant storage facilities. As a result, the development of stand-alone teleport devices seems to have ceased with attention being turned to close-ended transmat technology that would eventually culminate in the T-Mat (TV: The Seeds of Death) and its successor, the Interstitial Mass Transit System (PROSE: Transit).

Codes from Project Indigo were all that was required to reactivate the teleportation function on Jack Harkness's Time Agency wrist strap. This implies not only that the teleportation technology of the wrist strip, or in the housed Time Agency vortex manipulator, could be descended from Project Indigo, but more significantly, that the Doctor did not use his sonic screwdriver to physically damage the vortex manipulator when he disabled the teleport function, but had simply erased certain control codes from its memory.