The final aftermarket blind spot monitor on our list belongs to CarBest. This system comprises of two high speed frequency sensors that are mounted on the rear bumper and activated when the turn signal is in use. The sensors are accompanied by buzzer warning indicators as well as round LED lights that go off whenever a vehicle or an obstacle is detected. This budget friendly option has a rapid reaction rate and an 80-degree detection angle. It also comes with its very own installation kit and the sensors can be painted to match the color of the bumper.