V trackers are Visitors who are tasked with tracking people
V trackers are like humans in a crime scene, finding anything that belongs to the killer and finding the killer. They have the ability to find the target they are looking for, effectively.
V trackers have been noted to be extremely difficult to find, for that if released onto the Earth, it would be impossible to locate them. V trackers can find the target and alert the V's to disperse soldiers to apprehend the target. They have been also very effective at finding the target.
In Heretics Fork, after the V soldier was stopped in acquiring the hybrids parents, Anna commanded that a shuttle loaded with V trackers be sent down to the Earth to find those who were responsible. Joshua noted that if the V trackers are dispersed it would impossible to locate them all, and Ryan replied that the shuttle has to blown up out of the sky. However, Anna turned the plan against the Fifth Colunm by instead sending a V shuttle carrying dead human bodies to be shot out of the sky, so the Fifth Colunm would be known to the world as terrorists.