Here is a ready made solution, no need to learn Rasberry PI or code anything. You just plug it in (110 volts
OR usb 5 volt), then run the sensor. Alerts on high/low temps as well as high/low humidity. You can log in anytime/anywhere proactively or just wait for an alert. Will also alert you if the power goes out. I have 5 of these going back three years and they are very reliable. The max temp rating for these units is 125 Celsius (257 degrees and my furnace sensor mentioned below hits 140 degrees all the time). There are no monthly fees.
I have one on my overhead home theater projector. The projector is built into the rear wall with ventilation installed to keep it cooled. But I needed to know if the projector might get too hot as sometimes I watch movies in the afternoon in summer and i was concerned it might run to hot. The sensor came to the rescue several times when the ventilation fan was not working and the projector began overheating.
I have another one where I added a 15 foot cable to so that I could place the sensor tip into my furnace exhaust plenum (drilled a tiny hole in the plenum and stuck the sensor into the hole). I can monitor the health of my furnace easily from anywhere in the world. I know when it is on, what temp/humidity it is pumping out, etc. I can determine in the summer if the A/C is ‘blocking up’ from overuse. (Some people want it to be cooler than it can handle…). Lastly, the graphing capability of these sensors allows me to see any aberrant behavior instantly (furnace running for too long, temp output too high or too low, etc).
Does text and/or email and has a physical buzzer on it:
Here is a screenshot of the graph of my furnace sensor. I can easily see how it is behaving (again, the sensor is inside the main exhaust plenum just past the a/c coils and roughly 6 feet from the squirrel cage fan):