https://www.wired.com/story/apple-google-contact-tracing-wont-stop-covid-alone/

Apple and Google are offering a bold plan using signals from more than 3 billion smartphones to help stem the spread of the deadly coronavirus while protecting users’ privacy. But epidemiologists caution that—privacy concerns aside—the scheme will be limited use in combating Covid-19 because of the technology’s constraints, inadequate testing for the disease, and users’ reluctance to participate.

The Apple-Google proposal, announced Friday, is designed to record when two people come near one another without revealing their identities or location. It relies on Bluetooth technology, a short-range wireless protocol often used to connect phones to devices such as headphones.