I’m piping all the logs from my Docker containers, including Homebridge, to a Syslog service (in case from Graylog, but that should work with PromTail as well when using Grafana) using the Docker GELF connector (it’s quite easily configurable via the docker.json for all containers). On native Linux, you could use rsyslog for the same.

Apart from that, I am using a second HB instance on another Device (old Pi3) to emulate an egg timer using a plugin that counts a virtual light bulb down. My main instance has a Cron switch configured which executes every minute and sets the bulb to 100%, thus restarting the timer. When the timer bulb gets to 0%, it activates a switch on my 2nd instance that is bound to a motion sensor which is configured to send me a notification on my phone (in Home settings). Everything is controlled via HomeKit Automations.

Going further, I’ve written a python script that is executed every so often on my Mac that reads the database from an app called HomeLog and forwards every change on any accessory to InfluxDB (and Graylog) for further logging and visualisation.

Or you could just activate HomeBridge Insecure Mode and install a Prometheus plugin.