SMI Stay-In-Play on Ford Focus

Hank, SMI Duo does interface with the brake lights, and, in fact, if the toad is powered during tow, I assume the car's brake lights will come on when braking. On my Focus, the negative battery cable is disconnected (I put in a switch) during tow, and the car's tail lights during tow are additional bulbs drilled into the tail light housings. They are wired to completely bypass the Focus's wiring.

I'd recommend the installation video and the printed instructions, both available on SMI's website for more details.