A device built into the brain stem of every Vorta that lets them kill themselves on demand, intended to prevent capture and used by Weyoun 6.
The Founders engineered the Vorta to serve, and part of the design is a means of self-destruction. A Vorta who is about to be captured is expected to trigger the implant, which brings a quick death.
It features in the Deep Space Nine episode Treachery, Faith and the Great River. The sixth clone of Weyoun, activated after his predecessor's suspicious death, has come to believe that the war is wrong and defects to Odo. The Dominion at once activates a seventh Weyoun, who orders Jem'Hadar ships to destroy the runabout carrying them both.
With the attackers closing in, Weyoun 6 contacts his successor and sets off his implant so that the pursuit will be called off and Odo will live. He dies after receiving Odo's blessing, which he says is all he ever wanted.