I have the Compustar alarm system that includes a similar feature to the Chilly Dog. Rob (IA Solutions) installed a small thermostat on the bulkhead right behind the drivers seat. When set to the "cool" position, the van will automatically start and run for 15 minutes when the temp exceeds the setpoint on the stat. It doesn't control the A/C, but as long as you have the A/C manually set to blow, it will come on when the engine starts. After 15 minutes, if the temperature in the van hasn't come down to the set point it will cycle for another 15 minutes, and so on. With the thermostat set up, it will actually work on the heat side in a similar fashion. (Note that while the van is running in this mode, if you step on the brake without the key in the ignition, the engine will shut off.)
This option on the Compustar works very well. There is also another option that I have. The remote is a 2-way remote. It monitors (among other things) the air temperature inside the van and displays it on the remote. As long as you are within the range of the remote (specs say 6,000 ft, but I'm lucky to get 1,000 ft.), you can view the temperature and remote start the vehicle, if the A/C is manually turned on. Other than the range issue (Seems like everything including air particles interfere with the range) this pseudo Chilly Dog system works great.
I do have other problems with the alarm system however. The biggest complaint is that you can not put the remote in your pocket. It is so sensitive, and has so many key-code functions, that the jostling around in your pocket will say, start the van without you knowing it, or unlock it, or go into panic mode, or any of the other 20 different "features" the remote is capable of. To be fair, I could (if I remembered) to "lock-out" the buttons before putting it in my pocket, but I always forget or am too lazy to do this. I think it is just poorly designed in this respect.