I have built a completely autonomous drone....for £70!! Its an electric fixed wing based on an arduino board made of foam with a wingspan of about 1.4m and travels about 30mph. I can make it fly anywhere and at any height i choose by just clicking waypoints on a map and it will go and do it. I am a PPL holder and i only fly it where i can see and would fly any other model, usually any my airfield anyway, but if i can do that for £70 its a lethal weapon for no money. And when i say lethal weapon i mean any 14yr old kid who makes it fly at 2000ft just trying to learn something fun to something more sinister. As interesting as it is to learn how to do it, i can't help but think its quite scary.
APM | Open source autopilot