(WIBNI?)
The ESVTOL is an aircraft that can hover like a helicopter, take off and land VTOL-style (vertical take-off and landing, like harrier jump jets) and can carry any vehicle to an emergency situation very rapidly.
Unlike something like a cargo plane or a powerful transport helicopter, this
aircraft would be able to safely carry heavy loads (fire engines, ambulances, police cruisers, etc) to their destination in any weather and quickly, without having to worry about not having a runway. It would carry these loads with a computer-controlled hydraulic arm(s) underneath of the aircraft. An electro-magnet (like the ones in junkyards) could also serve this purpose (provided you shield the aircraft).
It would be useful in police chase situations because it could fly over the assailant's vehicle, lift it off the ground with the hydraulic arm(s) (or the magnet), and keep it immobilized while the police arrive. If the suspect(s) leave the vehicle, the police would be able to catch them easier (if they steal another vehicle, the ESVTOL will capture their vehicle again).
It would help firefighters by rapidly moving water to a forest fire or to a burning building, haul fire engines around (saving diesel fuel in the process, how about that?) and transport firefighters to a safe location rapidly if things get ugly.
It would be incredibly useful in an urban/city environment. There are more automobiles crowding the streets in cities and large urban areas, so getting an emergency response team to a site can take longer amounts of time. One easy solution is to carry their vehicle over traffic and drop them off at the site, and if necessary, transport them to the next site (like a hospital).
I know helicopters can do some of these things already, but according to Wikipedia, helicopters are both slow and unstable in windy situations. I would make the ESVTOL a fixed wing aircraft that would be similar to the Harrier II, except the take-off and landing in VTOL mode would be more automated, or at least mostly computer controlled, so pilots can be trained faster.
Second only to the VTOL ability, it would have the muscle necessary to carry something like a fire engine over a potentially long distance.
Summary: Use VTOL aircraft instead of current aircraft/helicopters to assist emergency service personnel, and make a single ESVTOL that serves all the emergency services, so it can fit any function need as quickly as possible.