Yep. Imagine a near future with a mothership balloon carrying thousands of drones the size of a deck of cards or so with a 20g explosive, gps, facial recognition, and something to detect cellphone signals and a small solar panel.
Drop a load over an area with the faces of targets preprogrammed into them and let them flit about looking for cell phone signal sources and if the face that's near the signal is a match explode on their neck.
Imagine releasing that over an airbase. These things can either attack immediately or just fall down to the area around and lie in wait recharging with their panel.
What's the counter to that?