Callisto Pulse

The Callisto Pulse was a device that could disarm micro-explosives up to twenty feet away.

River Song offered the pulse to Dorium Maldovar in exchange for a vortex manipulator that she required to reach the Eleventh Doctor. Dorium needed the Pulse to disarm the micro-explosives River had put in the glass of wine he had just drunk. The Pulse was in the form of River's earring. (TV: The Pandorica Opens)

Behind the scenes

 * According to Eleven Things You Probably Didn't Know About the Corsair, the Pulse was stolen by the Corsair from the Callistan Klepocracy on a covert mission for the Time Lords.