[gary_0]

I would absolutely not want to use a microcontroller or a complicated chip for something like that. Simplicity is the point.

[buescher]

Supervisor chips are not complicated. In some ways simpler than a homebrew analog watchdog, and the good ones will handle failure modes a simple watchdog won't, like those that result in an oscillating output.

[gary_0]

Yes, a simple purpose-made chip designed to be used in safety-critical situations, with high tolerances for voltage etc, would probably be better. Although one thing the 555 design has going for it is that a seasoned EE could take one look at the physical circuit and know exactly what it does.

But I would never trust anything that ran software for something like this.