If "Anti-lost alert" is enabled, your ZeCircle2 will notify you when the device paired with it (smartphone, tablet) will lose its Bluetooth connection (Bluetooth range: 10 meters).
You can enable this option in the Notifications section of your mobile application.
Once you are too far from your mobile device, the following icon 
will appear on your ZeCircle. As soon as you come close to your mobile device, your ZeCircle2 will connect automatically.