This is how the fences in Neal Stephenson's The Diamond Age work. The drones fly in a honeycomb pattern and are recharged in a mesh network with a few base stat

This is how the fences in Neal Stephenson's The Diamond Age work. The drones fly in a honeycomb pattern and are recharged in a mesh network with a few base stations flying around. Whenever a drone has a low battery it steals some power from its nearest neighbor, so the power gets diffused through the network without any of the drones needing to move out of position. If I recall correctly they just bunch up and push you away if you try to walk through them, but otherwise don't obstruct the view. Pretty fun stuff. :)