"We're also using the GPS features for other programs such as the Chicago Project for Violence Prevention using Nextel phones," Monahan says. "You can develop customized GPS apps that allow you to track people doing outreach work in high crime areas."

"Using mobile devices could be an ideal way to communicate with people directly affected, because more than 200 million people in the U.S. subscribe to a mobile service," says Ken Hyers, principal mobile analyst at ABI, a technology research firm based in Oyster Bay, NY.

But there are a few obstacles to implementing this and other mobile emergency alert services, not the least of which are subscriber-privacy issues, funding, distribution logistics and -- in the case of natural disasters or terrorist attacks -- the vulnerability of network infrastructure.

To get past the privacy restrictions, researchers say such a system would need to be "opt-in." Citizens would need to learn that emergency alerts were available, download the necessary applets, request a download, and subscribe in order to get updates. Thousands already opt in to some established mobile alert systems, such as text versions of Amber Alerts and terrorist alerts in Washington, D.C. Congress and the Federal Communications Commission could intercede in the future and automatically send alerts to all 200 million subscribers in the U.S., according to Hyers.

Infrastructure such as cell towers and the T1 Internet lines that the cellular network depends on proved to be more reliable during Katrina than many expected. In fact, many people text-messaged each other reliably during the hurricane, according to Hyers. He says that, in some cases, Verizon and BellSouth arrived at disaster sites in New Orleans and before FEMA. Often they were able to replace backup power on cell tower generators and get T1s back up and running.

Infrastructure and privacy issues haven't discouraged researchers in Japan, where mobile carrier KDDI, IBM Japan, and Kyoto University are collaborating on a real-time evacuation alert service for mobile phones. The service displays small readable maps and evacuation routes in the event of an earthquake or other natural disaster. A trial of the system is underway in Kyoto.