Lots of good ideas here.
I'll add one more. I just wired up my 2010 Honda CRV for toad duty. The Ready Brake is pulling the brake pedal, of course, so the car would be turning on the brake lights at the same time the RV is sending a brake light signal too. I cut the hot side of the brake light wire at the switch and added a relay. Roadmaster has this in a kit form but wants $20 to $30 for it. You can make the same thing from Amazon for less than $15. The Roadmaster kit "connects" the brake light switch to the stock wiring when the relay is on. I didn't like that either so I went with the fail safe method. When the relay is off the brake light switch is connected to the stock wiring. The relay I used is a DPDT 30 AMP unit. When the relay is on, the brake light switch is disconnected from the stock wiring but is connected to the other output on the relay. I set my car up with 6 pin socket, 4 for the lights, one for the charge line and 1 for the electric brake line. I don't need electric brakes on the car. My RV doesn't have an elelctric brake controller. I sent the output from the relay (when it's on) down the wire that is normally associated with the electric brakes. Under the dashboard of the RV I found the wire and added a T tap and a LED light. When the car is setup to be towed there is a switch that not only turns on the relay but also disconnects the fuse that we Honda CRV owners have to pull. The outout of the brake light switch now goes to the dashboard indicator in the RV. I can see if the brakes are working or sticking.
Fred