I run it to communicate with much more applications. It just depends on your own preferences. For example, some tools provide an API (local or cloud based) and you can directly plug in into that API. In The Netherlands you can read your electricity meter yourself by a "Dutch Smart Meter Readings" and DSMR integrates into Home Assistant with MQTT. I use Z-Wave as wireless mesh technology for lights and switches, the Z-Wave controller integrates into Home Assistant with MQTT.
MQTT is so easy to setup and configure, you can use it for any messaging you want. As an example, I run Home Assistant locally to run my home automations, but also check the status of my local devices and online servers (Digital Ocean droplets). One use case is my backup script which publishes the backup results to an online MQTT server, my Home Assistant checks the topics at that server to display backup stats locally. If something went wrong, Home Assistant notifies my directly. PS. The backup script also sends out e-mails which I filter in Fastmail, the success mails are trashed and only error messages are kept in the inbox ;)
I run it to communicate with much more applications. It just depends on your own preferences. For example, some tools provide an API (local or cloud based) and you can directly plug in into that API. In The Netherlands you can read your electricity meter yourself by a "Dutch Smart Meter Readings" and DSMR integrates into Home Assistant with MQTT. I use Z-Wave as wireless mesh technology for lights and switches, the Z-Wave controller integrates into Home Assistant with MQTT.
MQTT is so easy to setup and configure, you can use it for any messaging you want. As an example, I run Home Assistant locally to run my home automations, but also check the status of my local devices and online servers (Digital Ocean droplets). One use case is my backup script which publishes the backup results to an online MQTT server, my Home Assistant checks the topics at that server to display backup stats locally. If something went wrong, Home Assistant notifies my directly. PS. The backup script also sends out e-mails which I filter in Fastmail, the success mails are trashed and only error messages are kept in the inbox ;)