It assumes that BT is on because most people leave it on all the time. It assumes that the car has a BT interface because new cars do.
People use BT in their cars primarily for listening to music from the phone over the car's audio system, and secondarily for using the car's audio system for phone calls.
GPS plus other phones' GPS, and GPS plus map data, seems relevant?
Only if you are Big Brother tracking all the phones over an internet connection. Remember, GPS is a one-way radio signal from satellits not dependent on the Internet; any time you think "GPS tracker" you are thinking about an integrated system with map data, mobile data connections and active processing.
E.g. you could build something like that, and GPS would be part of the solution, but you can't do it all on a single phone no matter how smart it is. The phone knows how fast it is moving by knowing the time and a series of position updates; it might or might not have an accelerometer and a compass. It doesn't talk to other random phones in the area to find out if they are moving at the same speed, and if it did, every car in a traffic jam would be difficult to distinguish from the others...
no subject
People use BT in their cars primarily for listening to music from the phone over the car's audio system, and secondarily for using the car's audio system for phone calls.
GPS plus other phones' GPS, and GPS plus map data, seems relevant?
Only if you are Big Brother tracking all the phones over an internet connection. Remember, GPS is a one-way radio signal from satellits not dependent on the Internet; any time you think "GPS tracker" you are thinking about an integrated system with map data, mobile data connections and active processing.
E.g. you could build something like that, and GPS would be part of the solution, but you can't do it all on a single phone no matter how smart it is. The phone knows how fast it is moving by knowing the time and a series of position updates; it might or might not have an accelerometer and a compass. It doesn't talk to other random phones in the area to find out if they are moving at the same speed, and if it did, every car in a traffic jam would be difficult to distinguish from the others...