The Sonoff TH16 is a WiFi enabled smart 16A relay switch which can monitor temperature and humidity through the iOS/Android APP eWeLink.
With the latest eWeLink mobile application, customers can create a series of simple conditional statement (Smart Scene). This means users can use the Sonoff TH16 with the AM2301 and DS18B20 sensors (sold separately) to collect temperature/humidity data, which can be shared to some ITEAD smart home devices, such as Sonoff, Sonoff RF, Sonoff SV, smart socket etcetera. Thus, other devices set up a temperature/humidity condition to turn on/off connected appliances. This device works perfectly with electric fan, air conditioner, humidifier, smart fish tank, watering system and many other appliances.
The pluggable sensors are sold separately here:
Hackable for Advanced Users
The SONOFF devices are based on the ESP8266 processor that is supported by the Arduino IDE. In order to reprogram the ESP8266 a USB-Serial converter is required. There are now many projects and tutorials that show how the re-write the firmware.
One firmware that is very flexible and has good support is the Sonoff-Tasmota project.
Below is information regarding the eWeLink app