I have fitted sensors to the front of 2 previous cars and find that normally after market sensors only project straight ahead so would not pick up low kerbs ect.
However if you chose the mounting points carefully so the sensors pointed slightly downwards you would pick them up, the difficulty is that you would have no way of knowing if they pointed low enough, or even too low so they picked up the road surface, until they were fitted and then they could not be repositioned.
You would also need to carefully check over the gaps and accessibility behind the front bumper to determine where you could fit them and then wire them in to a switch on the dash.
