Though not a safety device per se, if I had a thermistor on the heater itself, I might be tempted to just connect it and set a maximum temperature for it, if only to have more instrumentation. (I'm kind of a fan of having instrumentation, as anyone who has seen the dashboard of my car will tell you.) Having more data available about what's going on is useful when something starts not doing what you think that it should.
As a shutdown trigger, I don't think that it can be compared to another one with the firmware, but it can have an upper limit for itself. If it were (As an example) 150°C, that's probably fine for anything up to a 110°C bed, but wouldn't give you nearly the warning for a 60°C target bed temperature, though a human watching the temperature graphs might notice a discrepancy if the heater was starting to lose good contact to the bed surface.
Human attention is one of the best (and worst) safety mechanisms.