You're not wrong but there are aftermarket direct TPMS that utilize Bluetooth to alert an App on your phone. These aren't very common and it's far more likely that someone is just tracking unique Bluetooth devices and not specifically targeting this very uncommon application of it.

Loosely related...

There are two types if TPMS, direct and indirect.

Direct TMPS use a battery powered sensor on either side of the valve stem to monitor tire pressure and transmit it wirelessly to the car's computer. They're very precise but rely on an expensive battery powered sensor on the valve stem, because of this they are less reliable, prone to failure, damage and tamper. You can identify direct TPMS by the green valve stem caps on a car.

Indirect monitoring leverages the tire speed sensor of the ABS or ESC systems to monitor drag induced by a tire with low pressure, it's not precise but it's accurate and far more reliable. And quite clever IMO.

The NHTSA instituted rule 126 requiring ESC on most vehicles, since TPMS and ABS are subsets of technology necessary for ESC, you should see all three features offered on most new cars today.

umm. green valve stem caps have nothing to do with TPMS. It's used by various places that fill tires with Nitrogen instead of ambient air.

gah... you're right.

Forgive me, both with oredog64, I was told it was the bluetooth tire pressure sensors. I am not familiar with the other systems.