"Merlins beard ...this is some map. Potter!"
-- Fake Moody/Barty Crouch Jr. (GF25)
The Homonculous Charm tracks movements.
Effect: tracks the movements of anyone within a certain area through the use of dots on a parchment.
References from the canon
The charm identifies the true identity of the person whether they are disguised as an Animagi, hiding under the Cloaks of Invisibility, or changed by Polyjuice Potion (PA17, PA18, GF25). However it does not distinguish between generations if people have the same name: "Bartemius Crouch" appeared on the Marauder's Map in Snape's Office and Harry couldn't tell if it was the senior or junior.
"Homonculus" seems to be a variation of the Latin homunculus (plural homunculi), literally "little person" or "tiny human artificially produced"