Aerial surveillance from satellites, or coming now from drones, or from airplanes has been used for decades. What we do is to keep up as much as possible with the technology. Drones have now been used by other departments, particularly National Defence when it comes to the military theatre. There are other forms of surveillance done as well to track vehicles and track individuals other than with their cellphones.
So yes, a multitude of technologies have been used with the aim of being capable of mitigating the threats coming from the serious people we are tracking.