Project Indigo

Project Indigo was Earth's first experimental teleportation device, which was reverse-engineered from the Sontaran teleport pod. The first person to test the prototype was Martha Jones. However, Jack Harkness highly disapproved of the device, saying that it hadn't been tested. Despite this, the device worked and teleported her to her mother's house.

Later Jack asks Martha what the two numbers that are oscillating are (they are 4 and 9). Jack then goes on to say that the was all he needed to get his wrist teleporter to work, so one can speculate that Project Indigo was the prototype for the wrist teleporter that the Time Agency used. (DW: The Stolen Earth)

Martha later used the device again to teleport herself to near a UNIT base in Germany. (DW: Journey's End) where the Daleks transmatted her to the Crucible after she nearly used the Osterhagen key