Emergency alerts are now international (since iOS 7). Governments now have the ability to send an alert to iPhones in order to alert citizen of impending danger.
The video below was recorded yesterday in the Netherlands during a monthly emergency audit.
The alert would be similar in your country, should the government find it beneficial to send.
Governments can take advantage of these alerts to warn of events like incoming tsunami threats, military strikes, and other dangerous situations that could spring up in a moments notice.
I can’t remember the last time I heard an air raid siren tested in Canada. I can recall one time when I was a kid, but other than that, it’s been decades. It’s nice to know the government can reach us before the zombie apocalypse hits full blown catastrophic proportions.