No need to run any cable through your firewall if you want to control add-on 12V accessories! But why?
To say that I am extremely thrilled with the Sonoff 4CHProR3 is an understatement! I actually have two in my Toyota Prius, one under the hood and one in the rear area under the floorboard.
Utilizing this setup, there is no “switch” inside of the vehicle, instead, I can either use an APP on my phone or the RF remote below.
You can customize the buttons, for example, button A controls the front roof light bar and ditch lights on the hood. D controls the Rear Lightbar and C controls my side LED lights.