I would hold off on this if I were you. There are rumors going around that the car's have already been wired up with parking sensors and that all Tesla has to do is turn them on. This seems to be confirmed by some D.S.'s but denied by others, but this may be what Elon hinted to by saying that 'for model S owners, the new thing is right under your nose already'. No need to pay for aftermarket sensors if ones are already installed.