Something like the Insitu ScanEagle is probably the drone closest to being effective for our application: http://www.insitu.com/systems/scaneagle/capabilities

However, they're still quite expensive and not really cheaper to operate than a Cessna, and then there are the legal issues. I personally think that once of the things that will drive the cost of drones down quite a bit will be when an autopilot maker comes out with a way to retrofit Cessnas and other proven, GA airframes into OPVs (optionally piloted vehicles).