doesn't cheap GM and Buicks have this already
Last I checked, I could not change my climate control or activate my seat heaters in the Buick Enclave nor Chevy Traverse using the OnStar app on my phone. In fact, the OnStar app doesn't even use the Wi-Fi, it uses a polling mechanism to allow you to do a remote start/stop, unlock/lock, panic/unpanic. It takes up to 5 minutes for the car to poll the servers for a command.
In the newest vehicles, OnStar does provide a Wi-Fi point as part of the communications module for access to the Internet, but it requires an additional data plan. if you have AT&T, you can add it to your share plan. (I laugh when I see the commercials showing 3 kids, each with a tablet, viewing a full-length movie from this device - that would blow through a month's worth of data in just over an hour.)
At some point in the past, Tesla spoke of offering a Wi-Fi access point but has not. The Tesla hardware has the ability to offer the same Wi-Fi access point, but it would require Tesla to figure out a strategy behind how customers will pay for data and how it will be measured. Tesla collects a lot of information from the car for improving its technology, and it's not just as simple as putting my car on my data share plan - because I'd be paying for Tesla's data collection. That's the biggest hold-up.