Otherwise known as CMAS... This was for a Tornado Warning. It sounds like the tone you hear on TV when there's a test or warning, except that the tone cycles on and off about 5-7 times. It's fairly distinctive. The alert is was displayed on the phone much the way notifications used to be shown (rounded edge box with text inside). It had a funky symbol in it... The text was explaining that there was a Tornado Warning for my area, take cover and the duration of the warning and to "check local media." What's pretty cool is that: a) the warning came about 2 minutes before the weather hit b) I got notified about 1 minute before the sirens went off. So, there's your confirmation that CMAS is built into the iPhone 5 - at least on Verizon. Don't remember if ATT is participating in CMAS. Don't look for the message to be in Messages - it's only in the Notification center.