May or may not build something but the last couple cars I've had tend to develop dragging brakes after a while. Probably doesn't help that I park on a dirt/stone driveway and live in a northern climate. My guess is there're a lot of people not getting the best mileage due to dragging brakes, maybe more than from low tire pressure before tire pressure sensors. My Hyundai drops from about 38 to 35 when I know I have a problem. Less than that if it's a smokin' hot problem. Anyway, I've considered thermocouples mounted on the calipers, thermistors and diodes, all requiring wiring back to a box in the passenger compartment. I'd like an IR solution pointed right at the rotors, but that probably won't be cheap or easy. Curious what the hive mind can come up with. Any cheap wireless solutions? Something that can be monitored on the phone? If the automakers did it, how do you think they might go about it? Also, anybody else suffer from this?