@alexsh1 Replace the FLASH in the Sonoff - easier in the latest models as they've put the FLASH chip on the back (Sonoff TH16 etc) - on the originals it was jammed in next to the programming button and a pain to replace.

So - I agree re: Sonoffs - we've written our own software at the tech blog and though not quite step by step it is easy enough to use and ROMS are available to save you having to get into compiling code. We use Node-Red and MQTT as the base of everything - so you have a number of ESP sensors and relay controllers etc all talking to a Raspberry Pi - or something much cheaper like an Orange Pi Zero running Armbian for example - and basically you're sending simple MQTT messages around the house - nothing has to go outside unless of course you want remote control at a distance. Modifying Sonoffs is easy - I'm sitting in front of some now updating them with our software - just in the process of figuring our which port is used for the second relay in the DUAL product.