I did get my phone app linked to the car. That was a whole ordeal... that involved Hertz maintenance supervisors.

The walkaway sensor is kind of like a virtual sensor made from multiple different components. Seat occupancy sensor, cabin camera, and bluetooth connection status are all used together to determine if you walk away from the car to lock it and turn off the headlights.

Something in that mess of components was broken because I found the car unlocked with the lights and heater on an hour later in the snow. Not fun when the nearest supercharger was fucking closed down. (On that note, wtf, Tesla?! The damn supercharger was on the map. Take it off the map if it isn't functioning!)