The cost is an issue. And the cost varies across the world.
https://www.amazon.com/TemperatureAlert-Cellular-Temperature-Monitor-TM-CELL400/dp/B003XP3LOG shows you the usual price I see on the base module and monthly fees.
i don't have a smart home system yet in my house, but would like to know of possible solutions for this, either standalone ad-hoc or via as part of smart home system.
i keep in my refridge a medicine which requires cooling (10 deg C) at all times. sometimes, due to power failures or other malfunctions the refridge might stop cooling. this can happen while I'm away from home for long periods of time. i want to get a notification, (i.e. possible via email / sms ) on such issues.
If possible this system should be wireless (including the sensor inside the refridge) and connected via the home wifi network.
thanks in advance.