Re: Cost?
If you're talking industrial drones they can get very expensive very quickly, but if you're of a technical bent you could spend a couple of hundred quid and put together something that can fly hands-off if needed. For quads you could easily build a few and send them up at an optimum time-spacing for maximum annoyance - I was also considering the feasability of a tiny petrol-engined fixedwing, which with an autopilot and enough fuel could get you enough loiter time to -really- ruin someone's day.
Biting the hand that feeds IT
