I'm sure there are other ways, but I use a SensorPush
sensor to monitor the temperatures in my freezer & refrigerator
(I carry some eye drops that have a very narrow storage temperature range) that connects VIA Bluetooth to my phone. It will send alerts for over & under temperatures, and can show hourly, daily, weekly, or even yearly graphs of both temperature and humidity.
The company sells a WiFi Gateway
that lets you tie it into a network.