We've lots of more or less cheap 433MHz Switchable Power-Outlets in the house, mostly for decorative lights. You get them for under 15€ in the Building Center, three at once with a remote control. Usually, you can control four switches with one remote, period. (A promising exceptions are the device from Intertechno.)
Now I was looking for a way to
First challenge now is to get the codes out of the remotes. For this purposes the rc-switch library provides an example sketch for the Arduino. I extended it a bit and got this:
Software for this thing can be found here https://gitlab.com/wolutator/433Receiver.git.
This is how it works:
The second challenge is to send the codes out into air and let the power switches receive them. This is done with this thing:
It is a Arduino Ethernet Board with a PoE-adapter and the 433MHz sender directly attached to it. I glued it under a table in the living room.
This thing received messages via MQTT and send them out via 433MHz.
The software is here at Gitlab.
BTW: do not expect beautiful software, this has been made on Halloween evening and night when waiting for the kids to come home.