I just bought my usb monitor off AliExpress and paid extra for the Bluetooth option. None of the manuals in the box mention Bluetooth at all. The app doesn’t open, just presents a black screen. I’m going to be asking for a refund. Also the Bluetooth module is too big and blocks access to plug in the device at all! Poor design, I’d say.

I had to knock a star off because I,too got the “unable to connect” and “ device not compatible “ error” when trying to link my BlueTooth to it. I found that you still have to open the app and from the first option “find” the device and swipe the toggle switch on THEN you’ll see it under your Bluetooth settings. Essentially... you’ll never use your iPhone settings to manage the Bluetooth connection to this thing. It’s all done within the app. I almost returned it until I blindly stumbled into that ‘fix’. Checking out the app though it seems to work very well. I got the UM34C so your mileage may very. Good features that work well. Exports data and a few triggers you can set and options I didn’t even know it had. So quite happy but the developer needs to either clarify the Bluetooth setup or make the setup work like every other Bluetooth device does.

Awesome! This uses a special minimal Bluetooth connection that DOES NOT REQUIRE ANY PAIRING. You simply grant Yes to Allow app to access Bluetooth and it magically connects! Easiest Bluetooth I’ve ever seen. I bought my UM34C from AliExpress for around $20 or less during a sale. ITS INCREDIBLE. I wanted one for so long and I don’t know why I waited this long! I’m interested in evaluating the U2-WEB, a more sophisticated competitor that’s priced around $30-$40 with a larger screen. ——Note:⚠️ Only UM25C bought from official Store before Dec 15th, 2018 support iOSThe AliExpress listing for the UM25C on "RD official store" states: "From china time Dec 15th, 2018, UM25C began support iOS app. If you buy it AFTER Dec 15th at RD official store, it supports iOS app. BEFORE 15th, it can't."

The app hasn’t been updated in 5 years. As such, it no longer connects to my UM34C. Looking at the reviews, it looks like it doesn’t work with anything running on a remotely modern IOS release. It is now effectively useless. They need to update this app.