You can add a number of difference sensors to the Sonoff devices. This document will describe how to add a DS18B20 temperature sensor.

The DS18B20 1-Wire digital temperature sensor from Maxim IC reports degrees C with 9 to 12-bit precision, -55C to 125C (+/-0.5C). Each sensor has a unique 64-Bit Serial number etched into it - allows for a huge number of sensors to be used on one data bus.

Wiring the DS18B20

Configuring the Sonoff

Retrieving the temperature via HTTP

http://sonoff/cm?user=<USER>&password=<PASS>&cmnd=status%2010

Ouput:

{
  StatusSNS: {
    Time: "2018-06-14T07:34:49",
    DS18B20: {
      Temperature: 21.8
    },
    TempUnit: "C"
  }
}

Integrating with MQTT

The temperature information will put published to the 

tele/<SONOFFDEVICE>/SENSOR

{"Time":"2018-06-14T07:56:34","DS18B20":{"Temperature":21.9},"TempUnit":"C"}

Setting interval at which the sonoff will report it's status

Display current interval

> TelePeriod

Set interval 

> TelePeriod <seconds>

Integrating with Homebridge 

Install the mqtt-temperature-tasmota homebridge plugin.

> npm install -g homebridge-mqtt-temperature-tasmota

Configure the plugin in homebridge's config.json file:

{
                "accessory": "mqtt-temperature-tasmota",
                "name": "sonoff98",
                "url": "mqtt://192.168.1.60",
                "username": "MQTTUSER",
                "password": "MQTTPASS",
                "topic": "tele/sonoff98/SENSOR"
        },

References