Despite it's intimidating shape, the Jet Spray is all about saving people. It's a conceptual tool to help firefighters put out flames in hard-to-reach places. Say, they really, really want to shoot some water on a fire just inside a window, but heat, winds or other conditions are keeping them from targeting it properly. In that case, they'd pull out the Jet Spray, a gas-powered gun that fires off a "remote nozzle" attached to a hose.
Once the nozzle lands inside the room, they turn on the water and the flaming area gets a full-on bath instead of the mild shower it probably would have gotten from regular hoses. Not a bad idea, as long as no one succumbs to the temptation to fool around with it in the off-hours.