I understand how it makes the decision to trigger the starter, but how does it stop operating the starter?
The light from the alternator goes off, that powers the relay that starts the car is powered by that light so when it goes off the relay is no longer active; the starter stops working. When the light is off the relay is off so the starter goes off.
What car do you drive? Is it a standard?, when you start you car does your alternator light just goes off or does it blink?, is there another light that clearly indicates your engine is not running but is off when it is? are you interested in trying this system?
Well, Effram has a manual transmission but is leased so I don't know that I'd do that kind of mod to it. My truck has difficulty starting due to some sort of pressure release problem in the fuel injection system, so I mostly have to leave it idling at stops (else I could tap the existing remote start system I previously installed). I'm mainly interested in fully understanding how it works.
I think in most vehicles I've driven, the alternator light stays on for a few seconds after starting...but I'll have to pay attention for a light that turns off as soon as the engine fires.