Story highlights Israeli developers create Red Alert smartphone app

It notifies users when Hamas launches rocket from Gaza

People outside the region use it to follow developments in loved ones' cities

Israelis looking to know when to take cover are turning to their smartphones to get real-time notifications after Hamas fires rockets from Gaza.

The Red Alert app co-created by Ari Sprung, an Israeli software developer born in the United States, has become increasingly popular as the conflict escalates. While the country's Iron Dome missile defense system intercepts most rockets, some do get through.

As a live interview with Sprung and CNN's Brooke Baldwin began Wednesday, both phones -- one in Jerusalem, the other in Atlanta -- sounded in real time as rockets were fired toward the Israeli cities of Ashkelon and Ashdod.

Sprung partnered with another Israeli software developer, Kobi Snir, after the 2012 escalated conflict between Israel and Hamas.

"We knew this would happen again, so we wanted to make sure we had an app ready to alert Israelis for the next conflict," Sprung told CNN.

Red Alert receives notifications when rockets are being launched from Gaza, and automatically sends out a push notification to users via the downloaded app. Their phone will play an emergency tone and display the name of the targeted community.

The free app is available on iOS and Android devices.

Sprung works full time at a software development company, and tends to Red Alert in his free time. The servers are hosted for free by ShartimIsrael, an Israeli web hosting company, he says.

For security reasons, the developers won't say how they get their notifications of rockets being launched. But they tell CNN the time delay is less than a second of when the audible sirens are sounded. At one point Tuesday, a rocket was being launched every six minutes.

Once the app is downloaded, users can select which Israeli cities for which they want to get alerts. Most users select "all areas."

Israeli officials and the Israel Defense Forces have publicly supported the app, and encourage people to download it.

Before the latest Gaza operation, there were 60,000 Android users and 80,000 iPhone users, all in Israel.

Today, Sprung tells CNN, there are approximately 290,000 Android users and 300,000 iPhone users worldwide, based on information from Apple's iTunes store and Google Play store. Of the 300,000 iPhone users, 250,000 are from Israel and 50,000 are in the United States and other countries.

The Android app isn't available outside of Israel due to limited server space; instead users with an Android device wanting to receive updates can do so through the "Yo" app

Gilad Harazy, an Israeli native studying in the United States, has family back in Israel, and keeps up with developments through the app.

"I want to know when it hits close by where my parents live," he says. "I know if it hits they won't be able to contact me immediately, so I want to be able to know to get in touch with them to make sure they're OK."

Harazy's family lives in the town of Nir-Banim, roughly 20 miles from the Israel-Gaza border. His parents have approximately one minute to seek shelter once the alerts go off, he says. The time it takes for Israeli's to seek shelter varies, based on how far they are from the Gaza border.

"It's great to be able to know on the spot when the alarm goes off," Harazy tells CNN. "In Israel, you might be in a closed room not near the sirens, so this new app allows you to know when something's going on. Although I'm happy to be able to know when rockets fall, it's really sad to know we need something like this."