In one of the most far-ranging attempts to halt the spread of the coronavirus, Apple and Google said they were building software into smartphones that would tell people if they were recently in contact with someone who was infected with it.

The technology giants said they were teaming up to release the tool within several months, building it into the operating systems of the billions of iPhones and Android devices around the world. That would enable the smartphones to constantly log other devices they come near, enabling what is known as “contact tracing” of the disease. People would opt in to use the tool and voluntarily report if they became infected.
https://www.nytimes.com/2020/04/10/technology/apple-google-coronavirus-contact-tracing.html

Also see:

Apple and Google team up in bid to use smartphones to track coronavirus spread
Apple and Google announced Friday an unprecedented collaboration to leverage smartphone technology to help trace and contain the spread of coronavirus.

The collaboration will open up their mobile operating systems to allow for the creation of advanced “contact-tracing” apps, which will run on iPhones and Android phones alike.
https://www.theguardian.com/world/2020/apr/10/apple-google-coronavirus-us-app-privacy