Hi Laurie,
I have the Safety Dave dual rear camera installed with the rear view mirror mounted monitor. It is fantastic. The car (2016.5 D4 HSE) is hard wired from the tow bar plug to the rear view mirror with a join near the mirror so that it can be removed. The monitor is a (very) tight fit over the rear view mirror. I've had the Safety Dave dash mounted monitors as well, but I don't like dash clutter and the rear view monitor is excellent.
Cheers,
Andrew