The myographic scanner of an escape pod of the Arcos
The myographic scanner was a sensing device that was part of escape pods, such as those of the Arcos.
The scanner monitored the bioelectric signatures of the crew in the event they were separated from the pod.
In 2367, Geordi La Forge modified the myographic scanner of an escape pod of the Arcos, stranded on Turkana IV, and installed a booster on the device that would relay its signals directly to the USS Enterprise-D. By doing that, the survivors of the Arcos that were abducted by the Turkana IV Alliance, one of the factions of Turkana IV, could be located.
When the away team beamed down to the escape pod, La Forge realized that the myographic scanner of the pod was still in working condition but the power source of the device was fluctuating. He ran a shunt from the converter and so was able to re-power the device and locate the hostages. (TNG: "Legacy")