It is no secret that I think MQTT has great applications in Model Railroading. With the release of inexpensive ESP8266 (and soon ESP32) WiFi MCUs and now the Raspberry Pi Zero W, I think we're close to reaching a tipping point which enables the wide deployment of affordable hardware.
Hackaday ran a nice series of articles on MQTT last summer. Excellent stuff.
https://hackaday.com/2016/05/09/minimal-mqtt-building-a-broker/
https://hackaday.com/2016/05/17/minimal-mqtt-networked-nodes/
https://hackaday.com/2016/05/27/minimal-mqtt-control-and-clients/
https://hackaday.com/2016/06/02/minimal-mqtt-power-and-privacy/
A video tutorial for creating a door-bell with push notifications is another neat tutorial video:
https://hackaday.com/2017/03/02/wireless-doorbell-hacked-into-hands-on-mqtt-tutorial/
The real challenge here will be making this accessible to "normal" hobbyists.
