I agree.. I'm trying to set something like this up myself. I figure I could use an old phone or cheap tablet with a cheap data package or free wifi. Rogers in Canada has a "Flex" dataplan for minimum $5.00/month for 10mb, which may be enough for simple data communicaiton like this. If I can access this phone remotely with another phone ( with say team viewer), I could get it's GPS location, and maybe internal car temp, and maybe with a bluetooth relay interface, I could start the car, the rear defrost, the blower, A/C etc. Even simply sending a txt msg to the phone, if the headphone jack could trigger a relay or opto-coupler connected to the Aux start input of my remote starter, that would be great.
Directed Electronics (DEI) makes a SmartStart interface as someone else mentioned, which interfaces to some remote starter systems they and others make (like Viper) I think it justs connects through a 4pin connector with +12, ground, TX, and RX ( maybe RS232?). If that is true, maybe a Raspberry Pi could be interfaced with it. The service fee for Canada is $70 for 1 year, and $150 for 3 years. These include roadside service, so not too bad a deal. Just not sure if the roadside is like or with CAA, or what the response times are..... I think with the Rogers Flex, it's like pay-as-you-go, and can suspend at any time.