SquareLoop got a boost in January when Morgan O'Brien, founder and former chairman of Nextel Communications, was named chairman of its advisory board.

There are different kinds of location-based technologies, but what sets SquareLoop apart is that it doesn't require any action on the part of the cell phone user, says Matt Vartabedian, research manager at iGR, Inc.

"If your geography changes, you would not receive alerts for the area you were not in," he says. In other words, people who live in Chicago wouldn't receive alerts about an evacuation of the Sears Tower, for example, if they were out of town for some reason.

That's not the case with other providers. Roam Secure, Inc. of Arlington, Virginia, also sends text-based emergency alerts via text messages, but it does not target an individual's location. The company's citizen warnings system, in place in 18 jurisdictions in and around the District of Columbia as well as Jefferson Davis Parish outside of New Orleans and the City and County of San Francisco, sends out information based on the home address of a wireless device.

Roam Secure, whose alerts cover traffic, weather and other emergencies, also operates systems specifically for first responder teams and for continuity of operations for government agencies and businesses.

President Harry Truman established the first national alert system in 1951. Its original purpose was to give the president a means to address the country in case of a national emergency, but by 1963, the system also transmitted state and local emergency information.

Since then, local emergency management personnel have used the EAS structure to relay local emergency messages via broadcast stations, cable, and wireless cable systems.

Earlier this month, FEMA distributed test messages over the Public Broadcasting Service's satellite system to local public television stations using a technology called datacasting, a one-way broadcast service that, when combined with an existing high-speed network, can stream video or transmit large files to thousands of locations simultaneously.

Public safety officials could use datacasting to pinpoint specific locations to receive messages and they could also use it to distribute information over a variety of media, such as cell phones, PDAs, pagers and computers. Datacasts are transmitted through a digital television signal and a receiver hooked up to a personal computer, laptop or computer network. The datacast receiver separates the data bits from the television programming stream, allowing this data to be manipulated and saved to any software program.