Uncovering a gunman’s position is traditionally a deadly game of luck and patience. This year, the U.S. Army gets help from the Ears system, a wearable, palm-sized device that weighs less than 6.4 ounces and can pinpoint a gunshot in less than a tenth of a second, even when mounted to a Humvee moving at 50 mph. The system uses a set of four microphones situated an inch apart to triangulate the origin of the gunshot. Software borrowed from submarine noise-detection technology analyzes the shape of the sound wave to determine the bullet’s precise angle. The results appear on an LED screen or as an audio prompt (“50 meters, 3 o’clock”). The device runs on less than a watt of power and lasts up to 13 hours on a single charge.