If you're worried about drones spying on you, the new phrase "persistent stare" coined by a drone manufacturer may make you feel uneasy. Its intentions are good, but let's hope its staring drone doesn't get into the wrong hands.
These drones can fly in place with no one on the ground controlling them. They're armed with video recorders and can fly up to 500 feet above you for an almost unlimited amount of time.
CyPhy Works, which created PARC (persistent aerial reconnaissance communications), describe it as a robot with unlimited time of flight. It was designed to provide long-term reliable communications, and what the company calls "persistent stare" capabilities.
PARC is tethered to a certain spot by a microfilament system. That's a fancy term for a very thin wire that holds it in place. It can fly up to 500 feet if it's tethered to the ground, but it can endure altitudes up to 10,000 feet.
PARC flies itself. The system includes a ground control station and a six-rotor VTOL (vertical takeoff and landing) air vehicle, the drone.