An Outlier droid was an android used for observation of a specific area from a far distance, taking the shape of whatever the inhabitants of said area looked like. Its eyes would occasionally flash blue, revealing its true identity.
One such android, in the form of a little girl, was employed by the Shakri to monitor everything that happened during the Year of the Slow Invasion when the Shakri, acting on orders from "the Tally", sent out cubes meant to rid the universe of the humans, which were considered a contagion.
The Eleventh Doctor's sonic screwdriver picked up strange signals from a little girl who just stood up and stared. When her face turned blue, due to interference, it gave her away as the android, and the Doctor shut her down. She was left lying on the floor afterwards. (TV: The Power of Three)