OK, if the power is out you wouldn't know the temperature. Although in theory you could build a battery powered cellular system. But like slfnflctd said, if i

OK, if the power is out you wouldn't know the temperature. Although in theory you could build a battery powered cellular system. But like slfnflctd said, if it doesn't report that the situation is normal, there's likely to be a problem. If there's no power and it's cold enough to matter, you go there (or call a neighbor or handyman) to either start a generator, start up a kerosene heater, or drain the pipes.