My 2014 Silverado has factory remote start, it turns on the heat or ac, the heated seats, and the rear window defroster. I can start it with my remote within a reasonable distance, or from my cellphone from anywhere. I'll never buy another truck without it!
Only drawback is it only runs 10 minutes, and I can only restart it once after that for another 10 minute run. If that could be changed it would be perfect! Since I work at night, it's awesome to go out to a truck that's warmed up with the ice melted off the windshield.
No experience with any aftermarket stuff though.