Tire Pressure Sensors
Automobiles have wireless Tire pressure sensors. This page stands as a reference page for research in regards to Tire Pressure Monitoring System (TPMS).
There isn't a standard for wireless communication but it is typically RF (UHF) and they typically communicate at 125Khz but also have chips that will communicate at 300Mhz-450Mhz. The Wakeup signal from the ECU is typically 125Khz and the communication back is on the 300Mhz-450Mhz range as modulated Amplitude-shift keying (ASK). They use the Manchester encoding  scheme and the packet format looks something like:
Primarily Identification. Tracking of vehicles while driving. Using the Uniq ID to trigger an IED when a target vehicle drives over it. Etc.