The GS-911 device can be left connected to the vehicle in a suitable position under the seat as explained in the Sleep Mode FAQ
If Battery Monitoring Mode is also enabled in the Setup->Options menu, the device will be woken up from sleep / low power mode every 24 hours, the vehicle battery voltage will be measured and this value stored to Memory Card. If upload of usage data is enabled and the device finds a previously configured WiFi Access Point available, the battery voltage value will be uploaded to the Hex cloud server.
The server can then compare the value to a preset threshold and the registered user notified via email when the value falls below the threshold. The threshold value is currently hard-coded to 12.0V but will be made customizable in the near future.
The push notification functionality of the battery monitoring mode should prevent the vehicle battery from being damaged by falling below a minimum voltage level if left uncharged for too long.