Which is why the Precise Flight standby systems include a low-vacuum
annunciator light.

Which merely gives you a false sense of confidence as the vacuum stays
on and the AI fails.

Since AI's fail as often as dry pumps (and far more often than wet
pumps) the low-vacuum annunciator light really doesn't help much.

The real solution would be a tiny magnet integrated into the vacuum
gyro and a tiny coil fixed in place. This would act as a generator,
and would likely make enough juice to keep an LED lit. LED goes out -
problem. Doesn't matter whether it's a failed AI or failed vacuum.

Now good luck getting that certified for GA at any sort of reasonable
price.

Michael