Sorry bro,
I got the electromagnetic sensor installed and it detects metals and non metal stuff both like somebody standing at the back of the car or some kid playing around in the garage! Also detected stone blocks some one had placed on the road to intimate a wicket!! Saved the bumper from getting damaged. Good thing is it's placed in "U" shape of the the entire bumper. So if i am reversing and any one comes closer from the sides I.e parallel to the car it beeps !!!