Anyone who has ever been to a big sporting event or a stadium concert knows that large crowds can quickly overwhelm local cell towers, making communication pretty much impossible.

Pro-democracy protesters in Hong Kong -- who need functioning phones to organize -- appear to have found a solution to this problem.

More than 100,000 people in Hong Kong downloaded an app called FireChat in a recent 24-hour period. The app allows protesters to keep chatting, even when their phones lose mobile network connectivity.

FireChat works by connecting users in a daisy chain, or mesh network, via Wi-Fi and Bluetooth. No mobile network is required, and users can choose to remain anonymous.

"With FireChat, it's completely decentralized," said Micha Benoliel, CEO of Open Garden, the app's developer. "And that means you can get connectivity from the people and devices around you -- directly."

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The benefits of FireChat have caught the attention of demonstration organizers, many of whom are encouraging protesters to download the app.

"Before you go near the government headquarters, please go to the App Store and download FireChat," Joshua Wong, the 17-year-old leader of a student protest group, urged supporters on Facebook. "Use this app to broadcast our situation to the outside world."

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Benoliel, who was in Hong Kong as protests escalated over the weekend, said the protesters were well prepared and well organized, and had anticipated that large crowds would complicate communication.

"They knew that at some point the cellular networks would be shut down or would just be overloaded by a number of people gathering in the same place, so they know that Firechat is a way to remain connected and communicate," Benoliel said.

While Benoliel said that FireChat was not designed specifically with protest movements in mind, it does seem to be catching on at demonstrations. In Taiwan, "Sunflower Movement" protesters also used the app earlier this year as they protested closer ties with Beijing.