Callisto Pulse

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

It later ended up in the possession of River Song. She offered the pulse to Dorium in exchange for the vortex manipulator she required to reach the Tenth Doctor. Dorium needed it 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. (DW: The Pandorica Opens)

Behind the scenes
According to The Brilliant Book 2012, a book that contains non-narrative based information: it was stolen by the Corsair from the Callistan Klepocracy while on a mission for the Celestial Intervention Agency.