The app Yo was released last April Fools' Day and many saw it as a bad joke. After all, the app's only function was to send people the words "yo" as a text message.
But now, developers in Israel have found a very serious use for Yo. They've used the code to let people around the world know when rockets are heading into Israel.
Android developer Ari Sprung says his original app Red Alert was in high demand because it sent alerts to subscribers' phones telling them to take cover. However, its own servers wouldn't be able to the handle the volume of users if people around the globe subscribed, too.
"So therefore we interfaced with Yo where every time we get an alert here, we send a Yo to every single person that subscribes to Red Alert Israel," said Sprung on Take Two. By tapping into the Yo app and its open interface, Sprung says they are able to convey what it's like living in Israel during this time.
"For our use, it's definitely solving the issue that we had in order to get that quick notification out to people without a lot of technical development," he says.