That MarCell Temperature monitor looks good but a bit pricey for me. I setup some old Iphones as suggested above. Downloaded a free app called Presence. I setup two phones that we can switch between watching. In front of one we put a large thermometer so we can monitor the temp. We didn't really need both phones setup, but since we had them we set the other up on the dogs bed so we can see them during the day. If the electric goes out the app sends a message saying that the phone has been unplugged. If just the AC would go out, then we can see that by the thermometer. I think this will work perfect for our situation and best of all it didn't cost us a dime!