Yes they are required on new vehicles and tire shop told me they couldn't sell me a set of wheels for my yaris to put snow tires without functioning tpms sensors by law. I thought that was a rip off. As far as aftermarket the only ones I've ever seen reviews on were the doran systems a lot of people run them on bikes not sure what they have for cars if they even have any but a lot of people are happy with the bike system.