Well, for existing cars, keep your key in a faraday cage.
My friend (who's not particularly technical and probably didn't know what a faraday cage was previously) told me that's what we has doing with his Prius key after it had been broken into with no sign of forced entry twice.
My friend (who's not particularly technical and probably didn't know what a faraday cage was previously) told me that's what we has doing with his Prius key after it had been broken into with no sign of forced entry twice.