Bit behind the times here, but how are cars even accessing this information, unless the phone is built into the car system, and the user has an cellular/data/wi-fi account with the car manufacturer?
All modern cars have cellular connectivity. The manufacturer pays the monthly fee. Since most cara have gps built in, they always know where you are.
When you connect your phone to the car via bluetooth or usb your phone will trust the car and hand over the data. Want to see that message on the car screen? Well the car manufacturer now has a copy of it. In real time.
"When you connect your phone to the car via bluetooth or usb your phone will trust the car and hand over the data."
USB charging I can understand, but seems odd that phones do not block data transfers (besides that needed to manage charging) unless the user explicitly permits it.
I guess people use Bluetooth to connect to car speakers, but again, why are the phones being so permissive with what they send?