* the node/homebridge/camera server evidently cannot add a camera to an already existing HomeKit key mapping. The camera def's need to be present when the bridge is paired with iOS. However, it is possible to change the cam url in the homebridge config.json.
* create a systemd service for homebridge as per the instructions here: https://gist.github.com/johannrichard/0ad0de1feb6adb9eb61a/ . If the homebridge setup was started and paired by starting manually before, copy the entire ~/.homebridge folder to /var/lib (not just the config.json), otherwise the already existing pairing info is missing. Don't forget to set correct perms/user/group on copied files. Also, make this service depend on "zoneminder.service" as explained here: https://stackoverflow.com/questions/21830670/systemd-start-service-after-specific-service
* the resulting script is saved as ''homebridge.service''. Commands are
** sudo '''systemctl <command> homebridge''' on ''zm''
=== ISY binding ===