Xiaomi Thermometer

The Xiaomi Thermometer is a temperature and humidity sensor with a Bluetooth Low Energy interface.

Xiami Thermometer

Properties

The device seems to use GAP to transmit data, so should be modelled using events not properties.

Property	description	range of values	operations
temperature	temperature value (`°C`)	operating range: `0` - `60`	`read`
humidity	relative humidity (`%RH`)	operating range: `0` - `99.9`	`read`

The page at https://pvvx.github.io/ATC_MiThermometer/TelinkMiFlasher.html also returns "Temp: 22.16°C, Humi: 61%, 2852 mV", so maybe battery status is also part of the GAP message.

Connect to the thermometer by clicking the Things and Resources category and then connect via WebBluetooth.
Select LYWSD03MMC and click Pair.
(optional) Give the device a name.
The device is now selectable on the webBluetooth device block in the Things and Resources category.

When the battery of the thermometer is low, the devices often resets and connection errors might occur in BLAST during execution of programs.

Apparently many Xiaomi devices also broadcast sensor readings via (encrypted) GAP advertisements, called MiBeacons, see https://esphome.io/components/sensor/xiaomi_ble.html.

To decrypt the advertisements you may need to put a "bindkey" on the device. See for an in-browser application https://atc1441.github.io/TelinkFlasher.html. To obtain the bindkey for the other Xiaomi devices see https://tasmota.github.io/docs/Bluetooth/.