Freezer & refrigerator monitor

At our farm, we have 6 deep freezers and 7 refrigerators. What Smart thing works best to tell us if one fails? I see similar posts which I will now read. Farm buildings are all 100 ft apart and all steel, or foil, covered, so I many need additional hubs. Apologies in advance, if this topioc has been covered

Is there a Smart Things temp monitor with wired sensor, so batteries could be outside? #20 wire would not significantly compromise the seal?