You’re talking science fiction now. If it becomes so small as a fly how on earth would it be energy sufficient? With a battery? And that battery will hold enough energy not only to keep it flying but also to provide for a taser that could incapacitate an individual? And at that size it should also carry some communication infrastructure to receive instructions from a command center, a gps, and a cpu capable of running face recognition or even detect movement patterns because otherwise you can’t have efficient crowd control. Sure, in a couple of generations we’ll get there, but not in the immediate future.

And 640K should be enough RAM for anybody. Betting against technology is a losing game.

My nephew has a palm-sized copter with remote that flies for 10 minutes, right now, got it for XMas.

There have already been dragonfly-sized gadgets made by graduate students. Check out youtube.

RFID tags are all the computing power you mention, already on your high-end product you bought from WalMart.

The future is clear. Maybe a one-use metal-air battery on a chip-bot? If I can say it, its conceivable.