In the end, the KIA car company made its cars into subscription models, I really hate this because in the end the car we buy with our own money doesn't feel like it belongs to us. Should we finally buy an old school car ? so as not to be affected by this subscription models or is there a way to crack the software installed in it ?
Then maybe don't make them rely on external servers? Your car has a computer, put the server there.
Even if all of the intermediate server tech is on the car, somebody still has to pay for the car's internet service, either cellular or satellite, it something.
Otherwise, you're not going to be doing remote start over IP.
This is only half the issue. You can put a server in the car, but that doesn't solve the networking issue. Most have a cellular connection now that needs to be paid for by someone. Then there is the issue of discovery. When you open that app on your phone, how does it know where to connect? Sure, it could look for a local or Bluetooth network. But that would only work if you're already close to you car like when it's in the garage.
Outside of that home network, something needs to facilitate the connection between your phone and the car. since neither will have a static IP address, it's essentially impossible to achieve without some server elsewhere to broker that connection.
Just package it into the car warranty. Most people wouldn't care then. For the most part new car people buy new cars and used car people buy used cars.
It's a really good idea for the car manufacturer, as it would add one more annoyance to buying a used car. New car, no worries unless you plan to drive it into the ground. Used car, now you have to go online to see what subscription costs might be.
But you have that, except on one central server.