In times of disaster, the easiest and most effective way of reaching the maximum number of people could be a text directly to their cell phones.

“Think about every day, what do you have on you?” FEMA Administrator Craig Fugate said in unveiling the agency's new alert system. “Most of us have a cell phone when an emergency is taking place. ... We need to adapt to what the public is using, not make them fit to what the system is using.”

That’s the logic behind PLAN, the Personalized Localized Alerting Network. The free service, unveiled Tuesday in New York City, will send geographically targeted emergency alerts to everyone with an enabled device in a specific area that may be threatened by a terror attack or natural disaster.

Fugate and FCC Chairman Julius Genachowski joined New York City Mayor Michael Bloomberg, commissioners of the NYPD, NYFD and representatives from four major wireless companies to announce this first national public safety system directly tied to mobile devices.

Calling it a 21st century version of traditional emergency broadcast alerts, officials say PLAN will provide vital information in real time to the people most directly affected, possibly saving lives in the process. On 9/11, for example, it would’ve been used to alert the public of the danger in lower Manhattan and might have helped firefighters who didn’t have interactive radios.

The system isn’t ready yet. It will be available to people with smartphones in New York and Washington, D.C., by the end of this year and will be online across America by next April. All new phones will come equipped to handle the alerts; others can be upgraded.

Officials say the alerts will be “very selective” and limited to issues requiring urgent action. Level 1 will be critical national alerts sent by the president of the United States. Level 2 will be warnings of impending natural disasters threatening lives. Level 3 will be amber alerts about missing or abducted children.

The special texts will also be sent with unique ringtones so they won’t blend with other messages or be easily ignored.

Bloomberg says the PLAN system “will provide clear and accurate information during the crisis, allowing people to receive specific messages alerting them to an incident in their area.” Officials also say they’ll provide a “fast lane” for the alerts so even if there’s network congestion the messages will get through.

But there is one major disclaimer: If you’re in an area without cell service, you’ll still be in the dark, so New York City subway riders, for example, may not hear about trouble ahead until they emerge from underground.