Does Zello work without Wi-Fi? What you need to know about the walkie-talkie app ahead of Hurricane

AUSTIN, Texas — As Hurricane Irma slams the Caribbean and heads toward Florida, walkie-talkie app Zello has climbed to the top of the iTunes App Store chart, the Washington Post reports.

According to the Austin American-Statesman, the app, which provided a crucial communication link between citizen rescuers and Houston residents stranded by rising floodwaters after Hurricane Harvey, is made by a little-known company in Austin, Texas.

Zello’s smartphone app essentially acts like a walkie-talkie, allowing users to send voice messages in real time to anyone listening to a channel. It requires Internet access via Wi-Fi or a cellular data network to work, contrary to false rumors spreading online.

During the flooding from Harvey, channels earmarked “Texas Search and Rescue” or “Cajun Navy SE” became popular with boat owners who used the app to find people in need of rescue.

In times of crisis, the app functions much like a police dispatch system, with crucial information relayed from volunteers who have spoken to flood victims in need of help. The app has a private chat function as well as open public channels.

Zello CEO Bill Moore said the app is more popular outside the United States, where some people use it as a phone call replacement or as a political organizing tool. The app is free to download; the company makes money off its premium version that it markets to businesses.

“Radio-style communication can be really efficient, and it’s such a great way to organize groups of people, which is the case with a lot of crises,” Moore said.

The American-Statesman wrote about Zello in 2014, when it received media attention for its use in political protests in countries such as the Ukraine and Venezuela.

That has made Zello an enemy of foreign governments on several occasions. At one point, the Venezuelan government blocked the app, and the government of Russia is currently trying to block the app, Moore said, though so far those efforts have been unsuccessful.

Moore said there are 100 million registered Zello users throughout the world, so the extra usage during Harvey wasn't significant for them. But Moore said there were "hundreds of thousands of people using it in the Houston area."

“The number of new users in the Houston area went up by a factor of 20,” he said, when compared to the week before Harvey hit.

Moore said he listened in on some of the Harvey rescue channels. “It’s riveting,” he said, describing a conversation he had listened to involving the possible explosion of a Houston-area chemical plant. “Emotions are high,” Moore said.

– The Cox Media Group National Content Desk contributed to this report.

Cox Media Group