Cocoon uses your smartphone as a 'key'.
When you come and go from your home location, passing through your localised geo-fence, Cocoon will know this, and this will be logged on the timeline in your app.
If all registered smartphones leave home, then Cocoon will arm itself automatically, simple as that.
Likewise, when you return home, Cocoon will disarm, and you can go about your day.
You can manually arm and disarm Cocoon in the app if you feel like getting a bit more hands on.