Lacrosse makes a great tool for this. https://www.lacrossetechnology.com/alerts/
Inexpensive. After the first year I think you pay $10 a year for the service but it will send you alerts for the temps you set cold and hot or if there has not been any data for a couple hours. I have a couple of these since we travel during the winter and also I use one to monitor my freezers to ensure I don't loose all my meat if one of them quits. The base for the unit needs an internet connection but the thermometer unit is wireless to the base. I think there in the $40 dollar range.
