Heat detector

Why doesn't Simplisafe have a heat detector for those areas where a smoke detector would false alarm?  I've tried talking to Simplisafe about such a device and it's always like talking to a brick wall.  As a retired engineer I know that I could gut one of their detectors and add a heat sensitive varistor or some other detector that could trigger alarm.  What puzzles me is why can't they do it or refuse to do it?  I've had the fire department tell me to remove the smoke detector in the garage last summer when a paving crew triggered it with hot top fumes.  I've had the smoke detector go off in my workshop while sawing wood, and I definitely would love to add a sensor in the kitchen that was insensitive to smoke.