Setup is pretty straight forward, turn it on and then scan in the Mi App or scan the QR code on the instructions and you'll be taken into the app within the smart humidifier section. Once it's in config mode, it will transfer the WiFi settings to the device, update the firmware and then add the device to a room.
The Mi Home app does allow automation so the humidifier can be turned on if the humidity (from another sensor) drops below a certain level. It would be nice if Xiaomi supported Alexa integration, but currently they don't seem to. There are 4 settings on the device, light, medium and dense fog and auto where the unit will detect the humidity and produce for appropriately.
Not all the Xiaomi devices are available in the UK and it's only possible to add devices in that are sold in the region you've set the app to. Unfortunately a lot of devices that are available from import sites, aren't available in the UK so the fix is to set your region to Mainland China and all devices will appear (it's still possible to use the app in English).
As well as humidifying the water, there's a UVC light source that sterilises the water as it passes through, so any nasty bugs shouldn't survive the journey (not tested). It holds 4.5L of water which is enough for about 12 hours use and it will shut itself off (and the LED turns from Blue to Red and in app) if the water chamber is empty.
The only downside seems to be that if there are PM2.5 sensors, they'll pick up the mist / water droplets and report them as pollution and reading can go well over 1,000 ppm (which is pretty polluted) and that may cause issues if automating on pollution levels.
Can be had for about £50 importing from your friendly Chinese site (inc shipping).