There's a really simple idea that's kind of a... why hasn't anybody done this yet? A simple abstract surveillance fence. A weave of drones + infrared + vision a

There's a really simple idea that's kind of a... why hasn't anybody done this yet? A simple abstract surveillance fence. A weave of drones + infrared + vision and other such tech (perhaps directional mics?) could create a highly secure border around an area. Uses would include states/nations, private households, company facilities, public works, maybe even things like sea observation (navy please stop running into things, preventing illegal fishing / human trafficking / drug trafficking / etc) and so much more. Seems like it would be a really fun problem to solve as well.