Signal-first refresh
The module is configured with interval: "once" and listens for SIGRTMIN+4. The daemon emits that signal after every state change, so Waybar redraws only when dots move.
State survives restarts
Every mutation writes JSON to $XDG_DATA_HOME/pinglo/state.json (override via $PINGLO_STATE_FILE). After a reboot the dots reappear exactly as before.
Flexible dot API
Besides the shell hooks, you can manage colored dots with pinglo dot set/remove, each accompanied by a tooltip and status that render left-to-right in Waybar.