I have come to believe that the least reliable piece of aquarium equipment is a heater. I have tried a lot of brands and have pretty much had heaters from them all fail. And the ones I have not used or had fail I have read about failing for others. My ultimate solution is to buy the cheap ones and consider them as "disposable."
When it comes to their failing they can only really do this in one of two ways, become too hot or fail completely. They overheat or do not heat at all. My solution goes beyond buying cheap. For my more expensive tanks I run heaters through a temperature controller. This willl usually prevent overheating and thus boiling one's fish unless the controller also fails. Unfortunately, a controller cannot fix a heater that stops making heat.
While I cannot say for sure, I would bet there are tank sensors that will detect a heater failure and send you a text or email. But these if they fail, you may come rushing home to save a tank only to learn that the sensor was what was really broken.
In the end the only way to prevent heater related disasters is human monitoring, and that is not realistic. In earlier times, when sites like this one were more active, you would have gotten many responses and probably rave reviews about most of the brands out there. There is no way to know whether a specific heater one owns will fail quickly or last for many years. I still have an E bo-Jaeger or two warming a tank for over 15 years. I have also had them fail in a few years.
Even having no heaters is not fail-safe. When you rely on the building heat to do the work, a power outage, or heating failure means can still get you.
"So many tanks, so little time. Since you can't get more time, you may as well get more tanks." Anonymous