Even simpler. If two of three conditions are met, switch engine off:
* Rising Carbonmonoxide levels
* No weight on driver seat for 3 minutes
* No driving activity for 3 minutes
The first factor alone should already prompt a shutdown though. It wouldn't even matter if the key was in the car, that might happen by accident and isn't a terribly good indicator.
I don't think this is actually simpler. I was deliberately trying to give an example that didn't require any new sensor tech. I don't think the cars have monoxide detectors right now.
* Rising Carbonmonoxide levels * No weight on driver seat for 3 minutes * No driving activity for 3 minutes
The first factor alone should already prompt a shutdown though. It wouldn't even matter if the key was in the car, that might happen by accident and isn't a terribly good indicator.