I have wired standard electric brake controllers in air brake trucks by using the air pressure switch for the brake lights as the controller input. The other wires were battery power, ignition power and a ground. The newer controllers are using inertia switches inside for the brake power after initial setup. If the trailer brakes are not aggressive enough after initial set up you can adjust the controller as needed. On several of the vehicles I installed the electric controllers on, they were going to continue hauling air brake trailers and had no issues switching between trailers and not interfering with any systems. I believe the cost was around $80 for a good quality controller.