My newest purchase is the so called Sonoff mini, a very small device that can build in a wall mounting box. The excisting sonoff software had to be adapted because this thing has no possibilities to connect a sensor and one can't see the leds on the board. Moreover this thing is equipped with an ESP8285.
The promising "diy mode" realy sucks. I had to connect the device and a laptop through an accespoint (mobile hotspot) that i had set on my smartphone. I could'nt use my normal windows 10 pc to establish the connection. This only worked on a laptop. Anyway, after some hours i saw the device in my diy tools app. Next i spent a half day to find out that it is impossible to flash software on it over the air. Nobody knows why. So i soldered 4 wires on the very tiny solder pads on the board and flashed them at the old way. This worked fine within 15 minutes!.
While adapting the software to work on the mini i introduced some interesting novelties. A.o. i made it possible to have 2 users, one (administrator) with privileges to edit the configurations and the other (user) can only operate the switch. Furthermore we can only connect a switch or a pushbutton to the mini. This forced me to find an other way to reboot and reset the device with the help of the switch/button.