Uncle Sam wants to text you — but only when there’s bad news.

The Federal Communications Commission has approved a plan to deliver emergency alerts to mobile phones via SMS. The messages will be delivered with an attention-getting “unique audio signature” and “vibration cadence.”

Three types of grim alerts qualify for the program: a national alert from the president, likely involving a terrorist attack or natural disaster; “imminent threats,” e.g. natural disasters such as tornadoes or university shootings; and child abduction emergencies.

Mobile device owners will be able to pt out of the program, and it’s possible carriers won’t charge for delivery of such messages. The plan is expected to go into effect by 2010.

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