The reason why wifi is unsuitable for what you suggest,
- Wifi requires a complex pairing process.
- Wifi requires your phone to connect to the car's wifi network (if the car had one), and your phone won't autoswitch. Even if Tesla implemented this, it would probably be worse UX than what we already have (going via the internet).
- Wifi also requires a more complex stack at the broadcaster's (the car).
The reason bluetooth is unsuitable,
- It requires pairing - which brings it back to "experience would not be much better than what you have now".
- It is inherently insecure to things such as DDOS or even brute force hacks.
That leaves bluetooth LE.
- This is actually suitable, very similar to how apple watch unlocks your mac when you are in proximity. But ..
.. proximity is a hit or miss, plus minus 10 meter accuracy
.. apple watch relies on touch, unlocked, and accelerometer to detect your movement to unlock your mac.
- So you could use bluetooth LE, but it still won't be automatic since proximity detection is a hit or miss. Connectivity will also be a hit or miss.
So long story short, using bluetooth or bluetooth LE, you could eliminate the need for internet connectivity. But you'd still need to connect to the car, start the app, and request to unlock .. so it can serve as a back up to no internet access. But not much more than that. I suspect Tesla may do this one day, but the return on effort here is very low IMO.
Now what Tesla really ought to do, is to stick a solar panel on top, and eliminate some load on the 12v battery. That would be a real improvement.
