Your auto guy is just plain wrong. I am not a major car guy, im pretty new to the whole DIY stuff. But I put in probably one of the most difficult remote start systems into my car by myself. You can read a write up about it on these forums.
First of all, I want to address boominbonne'* response. I have $5 that says your installer is completely wrong. If you have a semi new car, last 10 orso years with any form of VATS in it, which i guarantee you have because of the security light, then i am 99% positive it has to do with your remote start'* VATS module.
If you have the keys with the pellets on it, there are 15 possible resistor values for vats. What is probably happening is you are not getting the correct resistance in the signal sent to override your vats, or you have a bad connection to the vats wire (either of these means a bad install, and your installer should fix them for you).
I would suggest just getting one of the newer ones that auto learns the correct resistor value. $25 and 5 wires soldered in and your golden. If you have any questions about this, feel free to email me at email@example.com
The main point to bring up to your installer, is the security light itself. What that tells you is your car is trying to start, but because the VATS system is not being properly overrided, you are getting the security light. Usually there is, i think, a 3 minute cool down where your car will not start after that security light is set off.
As for the original message, jimzdat hit the explanation on the head. The only way that you could not start your car with a bad remote start would be if there was an issue between the wire that senses your key being turned to the on or run position, and the starter kill (which should be the only wire interrupted in any typical remote start installation). Even then it would depend on how the starter kill relay is designed to work. It may have its own "key in the on position" sense wire, which would mean it would not rely on the remote start system at all. The only relay then that you have to worry about is the relay for the starter kill itself.
One thing to note, any good installer will put in inline fuses for every 12v connection (every relay has one of these), if your getting an installation done, make sure they do that and solder every connection. This will guarantee you a much better, longer lasting installation. Then, all you need to do is keep a few extra fuses in the glove box and maybe a $5 relay if your really worried, in case there is an issue with your starter kill relay.
I personally have a pretty intense remote start system, and do not have a starter kill relay installed. Lets face it, not many car thefts in fargo ND
If your looking for a good remote start system, I personally would suggest compustar. I love my DEI 554r, but looking back, the extra $100 for the range would be worth it.
I would deffinately suggest getting a 2-way system. That way you get a response back when the car has started and your sitting in the middle of your house.
I would also suggest trying to find a remote with a vibrate feature, its annoying to have the beeps going off when in public.
My system gives me the ability to check the car temp, not a great feature, but nice. It willl also auto start at 0 Degrees. If i were looking again, i would look for a system that lets you set the temp it auto starts.
Another nicety would be a timed start, where i could say "start in 2 hours" so when i get back from class its all warm.
Hope this information helps out