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This conversation reminded me that many 1980s (and probably later) Volkswagens had a "dynamic oil pressure alert" system. It often ends up being disabled by owners when one of the sensors fails and it goes off inappropriately, but it was actually really clever. It used two senders, one that closed *below* about 0.5 bar (low pressure sender) and one that closed *above* about 1 bar. (The exact figures varied from car to car.) They fed a circuit board that was connected to the tach.
Below 2000 rpm, the high pressure switch was ignored. The oil light would flash if the low pressure switch closed. This also provided the bulb test feature (light would flash before you started the car.)
Above 2000 rpm, if the high pressure switch was *not* closed, the light would flash *and* a loud buzzer would sound.
The clever thing to me about this is the different levels of alert. At idle, if you lose oil pressure, you have a couple minutes to react before you do serious damage, so the light is sufficient. At speed, though, it's more like several seconds. That particular buzzer is not used for ANYTHING else in the car, so it's a loud and unfamiliar sound that immediately draws your attention.
This system saved the engine of a Cabriolet I had, when I blew an oil cooler seal one morning. Buzzer went off, I immediately shifted to neutral and coasted to the side of the road. There was still a small amount of pressure showing on the gauge when I shut down, but the oil dripping under the car was frothy, so the pump had *just* started to suck air.
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