If you are in an active task and your phone runs out of battery, or you turn your phone off, your task will still be ticking down on our servers. This means that if your active task runs out of time, even with your device switched off, it will still trigger an emergency alert. However, your device will obviously no longer be sending safety data, such as your location. Similarly, if you have an active emergency alert and switch off your device, the alert will continue.
It is important to note that your guardians will not be able to tell if your device if switched off - so make sure you keep your device sufficiently charged to ensure you are properly protected.