For fun! I think it would be pretty cool project to program those drones, etc. I'm pretty sure the security benefits would be low, and like someone else said, kids throwing stuff at it would suck. But then you can program in counter measure, maybe a water cannon, etc...

I've had similar thoughts. Another purpose your testing mobile security which you could potentially resell to businesses and eventually to the military.

build a dependable prototype that you could resell to business that have storage units, and someone with a warehouse that needs security, or a museum even.