The Sonoff is a small and inexpensive device to switch your electronics with WiFi.
Problem is taht the device does not support MQTT with the current firmware and is dependend on an online service in China.
This firmware replaces the original firmware and provides MQTT capabilities.
I was trying to build a OTA update feature. It worked well enought to deploay several sonoff switches around the flat. But then I saw that it broke 1 time out of 10 and now I have them installed and do not want to update the firmware even though I had made some interesting changes for configurability. Well, too bad.