When technology works
The real practical use of the Tesla phone App is so you can use your phone to lock/unlock or even drive it. No more looking for your key fob when you want to get something out of your car. Actually you don't even need a key fob at all, it's just a habit to use one. On the Model 3 you don't even get a key fob with the car, although I believe it's now an optional extra after people complained (I think mainly due to bugs with the App rather than the concept itself).