There does exist a current batteryless technology for tire temperature and pressure using SAW's which are remotely interrogated. A look at the Transense Technologies site will show how it works.

The problem to my mind is the integrating of the sensors into tire manufacture. To change a highly automated production line takes a lot of money. And how automated are tire factories, Continental are investing $100million in a new plant in Thailand - number employed 100. This heavy investment cost may be the reason that Michelin did not expand it's eTireII program.

For that matter does any large multinational tire company wish to take the investment jump when only one country currently requires the information. And the TREAD Act requirements are positively laughable in terms of usefulness and enforcement - and even safety.