Reading Voltages off Trailer connection on truck

Looking at putting hooking up truck (semi and pickup) trailer lights to an argon and use bluetooth to communicate with a second argon in the truck. Two questions:

Can I get away with a resister voltage divider to read the trailer lights being on / off, or do you think optical isolation is the way to go?

What is the thought on range from argon to argon via bluetooth? Think it will make it 15 feet from the back of a truck into the cab? I see this about range, is that all I need to know? Device OS API - Argon | Reference Documentation | Particle

This was only a circuit for trailing wiring testing, not for permanent use, but what I ended up doing was using a voltage divider, 47K to vehicle (V1) and 10K to GND, and connecting it to an analog input (S1). Just to be safe, I also added a D1213A 3.3V zener diode to the sense line in the middle of the voltage divider (S1).

The rest of the circuit is not needed if you are only sensing, but the schematic was confusing without that part.