Los Angeles officials on Thursday unveiled the first app anywhere in California that taps into the state's shake alert system, sending users a message straight to their smartphones ahead of large earthquakes.
But some key questions remain, like how well the app works and how much warning time does it provide?
The app, Shake Alert LA, is free and will give users 5 to 10 seconds warning if they live in Los Angeles.
San Francisco, meanwhile, is taking a wait-and-see approach.
For Bay Area seismologists, who have been developing an earthquake detection system for more than a decade, Thursday's unveiling in LA marks a huge step.
"It will save lives by giving precious seconds to you and to your family, to take action and protect yourself when the next 5.0 magnitude or greater earthquake hits," LA Mayor Eric Garcetti said.
Dr. Robert Allen with the University of California, Berkeley seismology lab said BART linked into the alert system back in October when it opened for business. Some hospital and utilities, like PG&E, also linked into the alert system, but not the City of San Francisco.
"We're certainly interested in the pilot program that they have in Los Angeles," said Francis Zemora, SF Department of Emergency Services. "And we look forward to evaluating the results."
Zemora said San Francisco studied mobile alerts a few years ago and was not overwhelmed by the results.
"One of the things we found was there simply wasn't going to be enough time -- to send out an alert through the mobile systems, to make it useful for people," Zemora said. "So what we focused on instead was a more direct connection -- automated alerts to critical facilities."
For now, San Franciscans are left to wonder if they want, or need, an LA-like app.