[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.

[buescher]

It depends on the system's potential failure modes and what's required by your safety standard, not on one engineer's opinion of what's "best".