At the Department of Defense's "Lab Day" last week at the Pentagon, scientists from the Naval Research Laboratory unveiled the world's smallest spy drone yet: a tiny, intelligent glider called the "Cicada." More formally known as the Covert Autonomous Disposable Aircraft, the Cicada is intended (like its namesake) to be deployed in large swarms—and to expire when its mission is complete.

It looks more like a maker project than a weapons system, but that's sort of the point. Designed to provide a low-cost way to drop dozens or hundreds of precision-placed sensors for monitoring everything from weather systems to enemy troop movements, the Cicada is essentially a flying smartphone that could be released in swarms from an aircraft or weather balloon, gracefully guiding itself to a predetermined target location in the air or on the ground.

Daniel Edwards, an aerospace engineer at NRL, described the Cicada drones as "robotic carrier pigeons." He told Agence France-Presse, "You tell them where to go, and they will go there." And upon their arrival, depending on the mission, the Cicada would broadcast sensor data back until its batteries expire—such as seismic to track traffic on roads behind enemy lines or adversary's movements and conversations picked up through microphones. There is also interest in non-defense roles for the Cicada, including collecting meteorological data from within storm systems.

The prototype of the drone was built for about $1,000, according to NRL's Aaron Kahn, but individual drones could be manufactured in volume for a quarter of that amount. NRL has already tested the Cicada in the wild, performing a test drop over the Defense Department's Yuma Proving Ground three years ago at an altitude of 57,600 feet; the miniature gliders landed within 15 feet of their GPS targets.

The Cicadas have proved surprisingly durable for their size as well: ""They've flown through trees," Edwards said. "They've hit asphalt runways. They have tumbled in gravel. They've had sand in them. They only thing that we found that killed them (on collision) was desert shrubbery."