Use the Bluetooth connectivity as an optional key to gain access and allow driving (i.e. no FOB).
Offer the option to log onto the Tesla website and enable/disable which paired Bluetooth devices will work. Options should include the ability to open and/or start the car when enabled. The car would always have Bluetooth enabled when this feature is active. When you get close to the parked car, your phone will pair as normal, and the car will unlock and be able to drive.
This has the added benefit in comparison to the current app remote start that you do not depend on a working internet connection for both the phone and the car.
Implemented in all new cars such as the Model 3/Y. Likely to be added to the S/X at some point.
I often lose my fob and drive with my phone. It's cold where I live, and I've often had to stand outside of the car freezing for several minutes, in one case even giving up and calling my wife to start the car from her phone at home. I do not have supportive thoughts of Tesla while standing like that.
As little as I care for having Tesla force me to stand in freezing rain, there is something worse on the horizon. When I drive into the city, I often need to park in an underground parking garage. It seems inevitable that some day I'll be several levels deep and in too much of a hurry to check internet connectivity before getting out of the car and letting it turn off. At that point, I will have the joy of having my car towed because there is no internet service that far underground and because Tesla didn't implement Bluetooth controls.
Cars aren't toys. It's not acceptable for things to work sometimes, even when you can plausibly blame someone else for a problem that you can readily anticipate. Aside from underground, there are many other places where the internet is unreliable, so you can readily anticipate that people will need to use the app to start their car where there is no internet.
Is it my mistake that I lose my fob or park without verifying that I will have internet service when I return? Possibly. So what? Is that how you design your cars? For example, will your self-driving features work correctly, but only as long as I don't make a mistake?
So fix it, preferably before I freeze to death waiting for a tow truck to come drag my Tesla around town hunting for an adequate internet signal.
A two factor option ie. BT device AND FOB would be much more secure to have keyless access! This would avoid switching off the FOB keyless access and giving back the comfort! Else there is a high risk for replay attacks.
This would be okay if it is able to be toggled off/on with a setting in the car. I guard my Tesla key, but my phone floats around too much and the last thing I need is for my phone to act as a key to the car.
Possibly, inside the Tesla app on the phone could also have the ability to toggle the feature. Thus, the feature would have to be turned on in both the car and the phone (with matching pins) before it can work as a key.
Bluetooth is too easy to compromise on its own. Tesla got it right by not allowing remote start without specific, new authentication, but could be better. This is not something safe to implement without additional strong authentication.