The Radar Jammer, or EC Jammer, is a gadget featured in Tom Clancy's Rainbow Six: Vegas 2.
A counter to the Radar Jammer, it effectively jams the GPS tracking as well as the shared battlescape (tac-map) of both teams in adversarial multiplayer. It lasts a short while, the stops working. However, you have plenty of "ammo" with this item. Much more than the GPS device.