A new app warns undocumented Americans (or people who are rightfully worried they might be accused of being one) about anti-immigrant raids so they can flee before the immigration forces come for them. Called RedadAlertas, or Raid Alerts, the app uses verified, crowdsourced data to sound the warning whenever the government sends U.S. Immigration and Customs Enforcement (ICE) officers to round up undocumented residents.

The open-source app was created by Celso Mireles, a documented citizen who was brought to the U.S. by his undocumented parents when he was a child. He spent 25 years living undocumented in the country. Mireles has been working on the app since the time of the Obama administration, but is now running in a higher gear thanks to Trump’s recent escalation of raids and promises to hire 10,000 new ICE officers.

[Photo: Don Kelsen/Los Angeles Times/Getty Images]

Mireles’s app is more of a service, delivering warnings in a low-tech way that can reach anyone, with any kind of phone–via SMS. In the future, it may add an actual smartphone app with push notifications. The system has two “levels” of users. “Group 1” is everyone who subscribes to the app. “Group 2” makes up the people authorized to report and verify raids. Those in the first group need only provide a phone number and a zip code. Those in the second group are verified using a combination of their Facebook profile and other “more personally identifiable information,” says the project’s wiki.

To trigger an alert, one person in Group 2 must report a raid, and then a number of other users must verify it. Preferably, one of these should be a user who is also a lawyer. Once verified, the alert goes out to all users in the vicinity, determined by ZIP code. As the user base grows, a point system that rates a user’s credibility will further safeguard against pranks and stop anti-immigration activists triggering false alerts. And that’s important because false positives could destroy the system: It only takes a couple of false alerts for people to start to ignore everything.

There are three kinds of raid reports–home raids, work raids, and traffic checkpoints. Only work raid and traffic checkpoint alerts will be sent out. “This is because there is little value in sending info about a home raid nearby, and serves more to spread fear,” writes Mireles.

This isn’t the first app that helps undocumented immigrants, people who face not only deportation but also discrimination and exploitation thanks to their precarious legal position. Borderwise is a service that helps immigrants apply for a green card–an excruciating and complex process with 40 pages of paperwork–and offers them a review by an immigration lawyer. It costs $500 a pop, a fraction of the usual cost of an immigration attorney.