Just as apps have seemed to reach the peak of frivolity (we’re looking at you, Yo), here comes a new one that could literally save lives in the most oppressive countries around.

Panic Button does just what you might expect from the name. Developed by Amnesty International in collaboration with iilab from an idea generated during an open competition, the open source Android app is a kind of secret bugle alarm for activists or journalists.

On a smartphone, the screen shows a calculator. Alerts can be set up to secretly transmit at timed intervals to rescue teams, relatives, Amnesty International or others. Panic notices – bearing text, the user’s coordinates, and a Google Maps link — can be sent by secretly pushing the power button if the user is being kidnapped or arrested.

“It probably couldn’t hurt,” GlobalSecurity.org’s John Pike told VentureBeat.

But, he added, it probably “works better in the movies than in real life.”

The reason, he said, is that real-world governments are often the enemy or an incompetent bystander. Take, for example, the three Al Jazeera journalists in Egypt recently sentenced to up to ten years in jail. “We know exactly where they are,” Pike said.

Or the dozens of young girls kidnapped by the terrorist group Boko Haram in Nigeria. “What passes for a pathetic excuse for a government in Nigeria,” he noted, “claims it has known where they are.”

Additionally, as the makers of Panic Button point out on their site:

Your country might be known to practise mass telecommunications monitoring and interception. If your profession makes you a target of this, then you should think seriously about whether using Panic Button will reveal information about your location and trusted contacts that could put you or them at increased risk.

But the app can help Amnesty’s efforts in other cases. One of the organization’s main tactics has been to shine a spotlight on those secretly kidnapped or arrested, sometimes bringing diplomatic or other pressure to bear even if the white-hatted cavalry doesn’t exist in that country.

“We have long known,” Amnesty Technology and Human Rights Officer Tanya O’Carroll said in a statement, “that the first hours after somebody’s arrest are the crucial window of opportunity for a network to make a difference to their colleague’s release — whether it be flooding the police station with calls, arranging a protest, or mobilizing lawyers and organizations like Amnesty International for a campaign of international pressure.”

Following three months of private beta testing with hundreds of users in more than a dozen countries, the Panic Button app is now available worldwide in four languages.