It is called the Cactus. Why so, I have no idea. They are about $40 for a pair, and once you have them, you attach a radio transmitter to your flash hot shoe and the receiving to your flash. Place the flash anywhere you want and you have wireless radio flash triggering.
Of course, you could just buy the unnamed, expensive radio triggers, and they really are worth the $400 or so if you need super reliability and other kinda groovy features, but those kind of folks will not read this anyway! I had given up on my pair of Cactus triggers. I had debated giving them away and just sticking with optical triggering (using the light of a flash to set off another flash wirelessly), but everything changed the past couple days. Here is what happened.