There is such a device that is attached to the rear of the bumper. Find that somehow there is interference and not necessarily effective or reliable. U might be better off putting in the ones that require drilling - the sensors can be painted.
can't remember the name .... there is a company that do leather seat on jalan sungai besi that sells them. It's a corner shop. MRZ Car Seats or something. Last inquired from them 2 years ago at the autoshow in PWTC