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 

Integrating with Homebridge 

References