I am new to the field of drones, and usually don't like hovering drones to monitor people's lives like a SyFy movie.
But I do think drones can be a cheaper and efficient alternative to many expensive alternatives.
A couple mentioned here:-

Usage 1:- Drones for traffic control. Taking 101 or 880, and an accident, and lane closures. Employ display boards at least 1 mile before freeway entry. Drones would have captured accidents on the freeway, and will calculate current delays via the current speed, and this will be displayed on the 'before-freeway-entry' points, so that commuters can decide to get onto the freeway or delay until accident is cleared.

Usage 2: California fire controls. Drones to pick up the direction, aerial maps of fires , some intelligence to be inferred on firemen mobilising, and entry-points to firezone for containment based on lessons learned on all recent fires.

In both cases, helicopter use for monitoring can be minimised., saving on expensive equipment and fuel

Usage 3: Can a drone detect a gun in a crowd? Can it also detect if the gun has been activated? If so, immediate measures could be applied even before a 911 call is placed, such as a security alarm going off, and alerting people.