Just reading this, which I thought might interest some of you:
It’s a 50x50mm (20mm deep) esp8266 board with a mains relay and power monitoring, which is an appropriate size for UK/EU light switches. A slight modification for dual and 4x relays shouldn’t be too tricky.
I’ve been on the lookout for a better retrofit solution (ie, keep my existing light switches). Zwave modules are working ok, but I have excellent wifi coverage inside and outside the house - same can’t be said for the zwave signal unfortunately.
The board is open hardware, but it’s a lot of soldering to put one together.
Anyone have esp8266 chips behind their light switches already?