First, the good news: The Sensibo Sky product works pretty well, at least if you own a recently-purchased Mitsubishi mini-split AC system. Since that is the only AC system that I've used the Sensibo Sky with, I can't say how well the Sensibo Sky works with any of the myriad other AC systems that are out there.One other bit of good news: If you send the Sensibo support folks a question, they will respond promptly with good, clear English.Now, the bad news: The Sensibo support folks may respond to your question with complete lies. This puts you, the buyer, in a tenuous situation at best.I have a Mitsubishi minisplit system, with four indoor "head" units. I want to be able to remotely control these units. That is exactly what the Sensibo Sky product (and other products, such as the Cielo Breeze) is designed to do.The Sensibo product consists of two parts: A small indoor device that you near your AC unit, and an app that goes on your phone. When you setup each indoor device, you use your existing AC remote control to "teach" it what kind of AC you have. Once taught, the indoor device will send infrared (IR) signals to your AC system. For example, if you want to turn one of your AC systems on, you open your Sensibo app on your phone, click on whichever AC unit you want to control (you need one Sensibo Sky unit per AC system), then click the "on" button on your app. This sends a signal through the Internet to the relevant Sensibo Sky device, which sends an IR signal to your AC system to turn it on. In the same way, you can set the temperature, fan speed, etc.All this works pretty well, as long as there is no power outage where your AC systems are located. A power outage is one of the most common ways for the Sensibo unit to become out-of-sync with your AC system. If your AC system was on when the power outage happened, the Sensibo app will think your AC system is still on when the power returns. But it won't be. Your AC system will be off. When you look at the Sensibo app on your phone, it will say the system is on. When you click on the app to turn the AC system off, the result can be unpredictable.Before I purchased the Sensibo Sky unit, I asked Sensibo support about this little problem, and they told me that they have solved this problem with a feature that will automatically re-sync the Sensibo unit with your AC. That's not true, and they know it. What the "sync" feature does is it allows you to manually tell the Sensibo app which state your AC is in .... but you have to be physically there, next to your AC system, to know this!After I bought the unit, I saw how the sync feature actually works, and I told the Sensibo Support folks that they had mislead me. I asked them if there was anything that could be done to ensure that the Sensibo Sky unit in sync stays with the AC system. They told me no.Again, this was a lie. The actual truth is that, if you own a modern Mitsubishi mini-split system, you can ensure that the Sensibo system is properly synchronized with your Mitsubishi system simply by sending two consecutive on/off commands via the Sensibo app. For example, suppose the Sensibo app says that your system is on. That might or might not be true -- you have no way of knowing if you are not physically present. You simply use the Sensibo app to click "off" then click "on". If the Mitsubishi system was already off, the first command will be ignored, then the second command will turn the system on again. After I discovered this (via extensive testing that I did), I pointed this out to the Sensibo support folks. They responded that they already knew this to be the case! Why they misled me twice in a row is ... beyond me.If you don't have a modern Mitsubishi mini-split system, the trick I described above might not work for you. It's all dependent on how the remote controls work for your specific system.Now that I know how this product works, I'm quite happy with it. My particular use-case is a vacation rental. Using my Sensibo Sky app, I can remotely turn the AC units on before my renters arrive so that my unit is nice and cool for them when they arrive. And after my renters leave, I can ensure that the AC is turned off so that I don't waste money cooling an empty rental unit. The same thing applies during the winter.The Sensibo company sells a bunch of other features that you need to pay for ($/month), but I am not using any of them, and I never intend to. As long as the Sensibo company stays in business and supports this app, I'll be happy.