on the 2014 Mazda 3, the rear bumper kit is quite lame. You pick the color, drill 2 holes, and plug it into the bumper. There are no existing sensors or electronics. In fact the sensor box has to be installed near the back rear left seat, and all it does is beep faster the closer you are from obstacles. So no integration with the back-camera or infotainment system to provide distances on the screen. The install instructions are also clear to align it very well to be efficient... so the install (drilling holes) is not fool-proof at all. A mechanic could screw it up easily.
All in all, the value is almost zero out of that kit.