I have remote starts in two of my vehicles. Both are programmable to start with temperature extremes. One is a long range RF but not connected to the internet. Two vehicles have CarPC's. With these PC's I have connected to the bus of the vehicles letting me tap into some basic functions like windows, lights, GPS. Having this ability, autostarting vehicle and internet access would allow you to extend your home HA to your vehicle if you wanted.
Integrating the autostart with your HA works with just about any remote starter / hack especially if your vehicle is in the driveway etc.
Things you have to be careful with are just saftey issues relating to starting your car remotely say in your garage without the door opened etc.
You can purchase GSM modules that will work with any sim card that will do what you want remotely (even GPS location etc).