We tow a 2015 Jeep Wrangler Unlimited, key off, doors locked and key in the coach. We plug the RVI brake into the center console/arm rest 12V outlet, it stays hot with the key off.
We also HIGHLY recommend Mopar's Tow Vehicle Wiring Harness made for the Wrangler. We had the dealer install it and its covered under the Jeep's factory warranty. Its turns the Jeep into a trailer (as related to lights). Its was $170+1.5 hours labor. It plugs into the Jeeps wiring harness and uses the OEM lights as trailer lights.