Comment by crustycoder

This is an old article and whilst there are undoubtedly still vulnerable vehicles, with the advent of UWB it seems to be a solved problem.

My car has UWB, there's a LED on the fob that blinks when it is in range and if it's stationary for a short time, it inactivates as well. Some experimentation suggests you need to be within about 5m of the car to open the doors.

The localisation seems to be very accurate, even if you can open the car from a distance it won't start unless the fob is physically within it. If I sit in the driver seat the fob has to be less than 10mm away from the outside of driver's window, otherwise it refuses to start.