I wrote an article a couple of years ago for the survivalist blog about drone detection and anti-drone technologies. I will try to link to it later. I mentioned something similar to this invisible shield but at that time it was million dollar technology - not for small private groups.
Most people are unaware of the threat that drones can pose to individual privacy and freedom, but just hang on.
From when I first read about drones, they definitely seemed a two edged sword.
ping me when you find the drones article!