To detect car back things , ppl make sensor with camera for safety driving .
Now there is hot item called bluetooth rearvirw mirror with built-in 3.5" TFT . driver could see caller when driving once ur phone paried with such device ,
When you place your car into reverse, it will Automatically engages into displaying by camera on 3.5" TFT.
It also Built-in dual stereo louder speaker, &
Built-in FM frequency transmitter connect to your car stereo,total 7 points available.
Although It's not a standard for car, It's necessory for safety car !