This is a housing for a NodeMCU and a relay board. The housing replaces the standard case of a light switch and is designed to be held in place by the switch itself, just like the original case from merten. This design eliminates the need for screws. There is an opening for the USB connector to provide power to the microcontroller. The baseplate has a slightly higher profile than the original, allowing wires to be routed from the light or shutter into the controller compartment.

I use this to control my shutters.