The Jalopnik guys are apparently out experiencing the thing, but basically it's a large water cannon like the ones used for those pumpkin shooting competitions mounted sideways in the rear of a V70R. The point is supposedly to test the effects of a side impact on a car without actually impacting it. Instead, the recoil of the cannon kicks the rear sideways. The resulting data is then used to design better stability control systems that minimize any further damage after an initial impact. But mostly, it's just a road rage defense system.