1. I believe that was addressed in the video. These are very short range devices that can be recharged by solar energy or by sitting on power lines.

2. See the video.

3. You might be able to deny access to buildings with mosquito nets but you're not going to stop close range surveillance, painting targets and other uses. Mosquito nets themselves would be relatively trivial to dismantle with a swarm of these (you'd only need to land one with explosives on the net).