AT&T began pushing an update to iPhone users over the weekend that adds support for Wireless Emergency Alerts. The WEA system sends text messages to smartphone owners alerting them to physical threats like earthquakes and tornados, man-made disasters, AMBER Alerts, and Presidential alerts.
AT&T pushes WEA update to iPhone owners
The update is being pushed to the iPhone 4, 4S, and 5, and doesn't require any action on the user's part since it's delivered over the air. Once installed, alerts will appear as special text messages and are delivered based on your location. For example, if an AMBER alert is issued for a missing child and you're in the same city, you'll see the notification.
The update is free, and since it's a carrier-supplied update, it won't appear in iOS 6's built-in Software Update feature.