Wireless Temperature and Humidity Sensor - Developed in The USA - 24/7 Data Logger with Alarm – Bluetooth Smart Thermometer and Hygrometer - Bluetooth Only - Not WiFi

This is a great product, and does exactly what it promised. The price is currently a little bit steep (~$40) per unit when compared to others, but you get back a well working and useful device. The Bluetooth range is incredible, even with the signal blocked by stainless steel doors.The reason for this purchase was a kitchen refrigerator and freezer combo that appeared not to cool well, or at least very inconsistent. Before purchasing two of these units, we cleaned out the coils located under the combo that were full of dust. First with a coil brush to get the biggest dust bunnies out, then a final clean with a battery powered little leaf blower (Makita). The leaf blower did the trick and made everything look like new. This required unplugging the combo and removal of back plate to make compressor area accessible for cleanout.Moving on from cleaning the combo, I reviewed multiple solutions of how to monitor temperature in both refrigerator and freezer compartments. First I was set on some high grade mechanical temperature meters, but after thinking about it for a little longer I didn't want to have to open and close the doors all the time in order to see what the temperature was. Also, the temperature is always moving down when the compressor is running, and up when it is not. The refrigerator and freezer operate in a bandwidth, and when it is equipped with auto-defrost you might think the freezer is not working while it is just cycling through a defrost cycle.Then the sensor itself; I'm tech savvy due to my profession as an engineer, so I typically try to buy quality over quantity. First thing I did was checking it's accuracy with some lab grade equipment, and readings were well within 35% of the maximum allowable tolerances (see specs). These units can easily be calibrated via the app, which I did, although they would have been fine without these minor adjustments.The app is easy to use, and has hourly, daily, weekly, monthly and yearly graphs that show min/max and average for selected time range. There is an option to download all data points to a computer or your phone. Very useful to see performance over time, and whether or not it is time to clean the coils. With an auto-defrost feature, you'll be able to tell exactly how many times it runs this feature. If it starts happening more often, you may have door seals that are worn, or usage might have been going up (open door more often, and this cycle runs more often. It was a surprise seeing the freezer go up to 41°F about once a day.That gets me to one point of improvement I would like to see in the app; there needs to be a delay that can be set before it warns you when temperature reaches a certain level for a determined time. For instance, I set my freezer alarm at 9°F. I want the app to notify me only when the temperature is above this temperature for more than 2 hours. Currently, I get notifications every time the auto-defrost cycle is running, which leaves temperatures above 9°F for a little over an hour. For this reason I had to remove the alarm, or basically set it at over 44°F, which now will not warn me anymore if freezer contents are over 9°F for an extended amount of time.Last thing I would like to mention is that you'll need to give the app continue location access, which is only related to Bluetooth access. You can turn it off to allow only when you open the app, but it would then not give you an alarm anymore unless you open the app. Without alarms set you could just give access only when the app is open.This item is definitely a winner, but I still hope Tempi.Fi will add a delayed alarm feature to their app so it can be used in refrigerators or freezers with auto-defrost function, or to limit alarms when loading groceries. It comes with double sided 3M tape, but instead I used "3M Dual Lock" velcro so I easily can take the units out when replacing batteries (they should last 1 year). Perhaps another improvement idea. I hope their will be a gateway soon, as they state they are working on it, and it would allow for temperature checks wherever you are.

Excellent! super easy almost automatic install on Android, just made sure the device is right on the surface of your mobile screen, inside the small square area designated for it. It take temperature very good, the connectivity is super good, and the graphics are nicer of what expected.

I started out with one of these for a terrarium then a couple for my humidor’s and so on. They work great the factory setting for the temp has always been right on. I have adjusted the factory setting for humidity slightly on a couple, once I have done that they work great.I set one of the sensors to an accurate temp and humidity then use it to adjust the humidity on any new one I purchase.HIGHLY RECOMMEND

I bought three of these (T1 hardware) in May 2021, so I've been using them for almost two years now. I have one in my attic, one in the basement, and one in my freezer. I've never changed the batteries and the app is still showing them at full power, so the battery life is excellent.They were a great solution for me, since I was concerned about heat loss/gain through the attic, humidity in the basement, and the cooling ability of my very old fridge (1988 vintage). The Bluetooth signal is strong enough to receive with my phone basically anywhere in my house, though the fridge signal is weakest. The on-device datalogging also means that I don't lose any data when I'm away from home, even for up to a few weeks. Also, while the accuracy of the measurements is +/- 0.3C and +/- 3% RH, the resolution of these readings is much better -- 0.02F and about 0.04% RH. Since the readings are low noise, this means that you can see even very subtle trends, even if the absolute accuracy isn't that great.The biggest weakness, predictably, seems to be related to the software. The app has last been updated over a year ago and has a grand total of three releases on iOS. So I'm not seeing a big commitment to stay on top of OS and device changes and no vision to expand the capability of the app over its base functionality. The functionality is okay for what it is, but could be so much more with this data collection capability. You can't see current readings for more than two devices at a time or the reading history for more than one device, and the app doesn't remember your display setting for the history plot for a device if you switch away from that screen.Further, I can think of a lot of advanced capabilities that could be built into the app, such as the possibility of calculating building heat loss/gain in combination with a feed of the local outdoor temperature or detecting low refrigerant charge in refrigerators and freezers based on the cooling rate after a defrost cycle. You can easily export all of the data to CSV to do whatever you want with, but I think a lot of people would have a use for advanced processing but lack the knowledge to do it themselves.The only issue in particular that I've had is that sometimes a sensor won't properly update the software for a period of time. This will show up as a jagged line in the software, as relatively few points have loaded. I've found that quitting the app and restarting it will cause it to redownload the missing data as long as you catch it within the memory period of the hardware. It has only happened to me two or three times in the almost-two-years I've used the sensors, so it's not a major issue.Tempi.fi has also apparently come out with new hardware revisions, T2 and T3, but has not published any info about the changes. It might only be form factor, since it appears they now offer a choice in the positioning of the lanyard hole. While the tempi.fi can be single-point calibrated to offer somewhat better accuracy, other similar devices, like SensorPush, offer better accuracy out of the box and, in some devices, even pressure measurement. That comes at a higher price, however. SensorPush also has a gateway for sale if that's something that matters to you, while Tempi.fi's gateway is still nowhere to be found. I haven't used SensorPush's hardware or software, though, so I don't have any comments about its usability or longevity.In all, the Tempi.fi hardware works reliably and produces valuable data. I just wish the company were more proactive with updates and features.