I'm going rogue on it until I think of something that makes sense to me.
Oil pressure switch is the most common but I don't have one of those as I use a mechanical oil pressure gauge. And these only work if your engine dies in a wreck...which generally speaking does happen but may not. In 1971 a friend and I came up on a wreck involving a Fiat Spider...driver was dead and engine was still running. Running very fast, in fact. The car had been hit with a glancing head-on blow that struck right behind the driver's side wheel and had been either knocked out of gear somehow or the driver struck the shift lever in the impact. We later wondered if it could have been hit hard enough to just separate the driveshaft from the transmission. Aside from the area in front of the point of impact it was a horrific mess.
A mercury switch is what I've seen some folks use (if you flip the vehicle over it breaks contact in the fuel pump circuit...but it seems to me if you flip over and over you can presumably land right side up and then you could catch fire or explode anyway. Seemed to me a scheme Ford Pinto engineers might have thought made sense.
And there are inertia switches. Another "better" Ford idea which hasn't worked nearly as well as the person/people who came up with it probably hoped it would. From what I've read they fail fairly frequently and can be tripped by anything from a pothole to a speed bump to driving on a flat tire. With the smooth AD suspension I can see these things being tripped by driving down a gravel road. So, I don't know. I should do something but I haven't decided what.
