https://techcrunch.com/2020/12/07/californias-ca-notify-app-to-offer-statewide-exposure-notification-using-apple-and-googles-framework/

The state of California has now expanded access of its CA Notify app to all in the state, after originally deploying the app in a pilot program at UC Berkeley in November, which later expanded to other UC campuses. The statewide launch of the app, announced by California Governor Gavin Newsom on Monday, means that the tool based on Apple and Google’s exposure notification API will be available for download and opt-in use to anyone with a compatible iPhone or Android device as of this Thursday, December 10.

Apple and Google’s jointly-developed exposure notification API uses Bluetooth to determine contact between confirmed COVID-positive individuals and others, alerting users to potential exposure without storing or transmitting any data related to their identity or location. The system uses a randomized, rolling identifier to communicate possible exposure to other devices, and individual state health authorities can customize specific details like how close, and for how long individuals need to be in contact in order to quality as an exposure risk.