Given the threat of cheap drone swarms coupled with increasing domestic disruptive activism, protective counter drone swarms are needed at events and facilities. Sports stadiums, large outdoor public gatherings, religious buildings, critical infrastructure will need either periodic or permanent drone coverage capable of interdicting attacking hostile drones/swarms. These should be autonomous given the likely extremely long periods before an attack but the requirement for constant vigilance.
Threats are now coming from the 3rd dimension, so traditional walls and barriers supported by human security is going to be critically deficient in the future. An option would be to have a mobile ground sentry with single or multiple aerial drones that it can launch as needed.
It addresses new vulnerabilities as adversaries take to the skies in numerous and anonymous new ways. The active security will be more obvious than traditional barriers and security cameras.