I do this with a $5 ESP32 and a reed switch and some simple code — in my case, listening on HTTP and returning opened/closed depending on the state of the reed

I do this with a $5 ESP32 and a reed switch and some simple code — in my case, listening on HTTP and returning opened/closed depending on the state of the reed switch. Just throwing this $7 option out there though I recommend just getting some pre-built thing in this case.