Deadly tornadoes and other disasters often leave many victims isolated, unable to reach families and friends. Scott Tatum was stuck on a Mississippi road when a killer twister barreled down on his truck last month.
"I tried to make a phone call, but could not get a signal through. I tried to send a text, but could not get a signal through," he said. "It was pretty frightening."
But using the Life360 application on his smart phone, Scott was able to check in, and communicate almost immediately -- with the touch of a button -- letting his loved ones know he was okay.
"It gave everyone a lot of relief," Tatum recalled. "My family knew where I was, and felt much better about it when they got the check-in."
In recent years, several so-called disaster apps have become available, including Guardly, Emergency Distress Beacon, and Quake SOS.
With 3 million subscribers, Life360 is used mostly by families to track their kids. But it can also turn smart phones into utility tools.
"We have servers literally all over the world that can access long-distance lines, send text messages a thousand times a second -- you just can't do that as a person; but we can, as a technology company," says Life360 CEO Chris Hulls.
Hulls says he developed the free mobile app after Hurricane Katrina left thousands without a fast and effective way to confirm they were safe.
At company headquarters in San Francisco, analysts are able to track when and where storm victims use the app. In the most recent disasters, data showed hundreds of people, even in the hardest hit areas, were able to send "I'm okay" messages, or activate panic alerts.
Maps show hundreds of people checked in on Sunday after the tornado struck Joplin, Mo., including a few who activated the panic alert system because they needed help.
And after the recent floods inundated Memphis, more than 2,000 families shared their location and confirmed their safety. Engineers are now studying the usage patterns to help improve the technology.
No one wants a disaster. But when they're in it, users say they're grateful for mobile personal safety apps, a hi-tech lifeline for their families.