1btn is a Battery Powered Open Source ESP8266 WiFi Button - CNX Software
2x Wemos D1 Mini Shield IoT Wireless Button for ESP8266 WiFi WeMos Module | eBay
Use NodeMCU to send push button signal to remote MQTT client – kookye.com
Simple IoT Remote Switch With MQTT and ESP8266 : 4 Steps (with Pictures) - Instructables
GitHub - garthvh/esp8266button: An IoT Dash Like Button using an esp8266, a push button and GitHub Actions. Tested on an Adafruit Huzzah, SparkFun Thing, and Wemos D1 Mini