In war, your biggest problem is collecting clear, accurate intelligence on the enemy: what they’re doing, what they’re armed with, turn-ons and turn-offs, favorite movies, that kind of thing. So the Army has decided that its next advancement in passive intelligence gathering is…a rock.
Not just any rock. A spy rock.
It works like this: palm-sized collections of sensors, usually seismic and acoustic sensors, are left behind inside fake rocks by US ground forces. The “rocks” have solar panels built into them that allow the sensors to recharge. Normally, these sensors are pretty much in total shutdown: if nothing’s happening, they’re basically dormant.
But if they detect motion, they might, for example, send a signal to a nearby spy drone, who can check out the situation. Or, they might broadcast a short message to the nearest military unit, letting them know something’s up.
Furthermore, they can be used to create “mesh” networks, meaning that the rocks could track a specific seismic signals across long distances by networking with each other and comparing the acoustic signature.
In short, if you’re a terrorist: fear rocks.
This Rock Could Spy on You For Decades [Gizmodo]