I have a foreign based teflon like substance which does indeed prevent stonechips from happening (unless they are too bad as I have 1 stone mark on the front bumper now - but 4 years without a single one).
The UK based treatments are indeed not worth anything, but I did pay about €600 for mine which does mean never waxing the car. In case of accident damage, they do re-apply for free as you have a lifetime warranty (except a long way to travel ...).