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Tesla making it easier for you to find your lost car keys

Possibly also to know if the key is in the car vs outside the car. It currently doesn't do that, which I find lacking.
I was surprised when I found out that it couldn't tell where the fob was. In the Prius the car knew exactly where the fob was and if it was outside, even a little bit, it would not start.
The Model X uses triangulation to detect that you are walking towards the front door from behind so that it can open automatically. Maybe this new key makes it easier / faster / more efficient to pick up the signal and your exact location?

I think this is exactly the reason for the switch to Bluetooth LE. MX needs to know where the key is and how it is moving in order to open the door. If it has two or more receivers on each side, it can measure the difference in signal arrival time and approximate the angle of where it's coming from (and distance from round-trip time). So it could tell if the key is approaching the door from the front, the rear or directly from the side. This technique is called "beamforming".

It's much easier to do this if the wavelength of the signal is smaller than the area you're trying to deal with (meaning it has multiple waves to deal with). The wavelength of Bluetooth signal is 12cm (5"), but the wavelength of the old style remote is 1m (3'). It's much easier and more precise to deal with the former than with the latter.