BBC News:

The BBC has learned that NHSX – the health service’s digital innovation unit – will test a pre-release version of the software with families at a secure location in the North of England next week.

And:

People who have self-diagnosed as having coronavirus will be able to declare their status in the app.

The software will then send the equivalent of a yellow alert to any other users who they have recently been close to for an extended period of time.

If a medical test confirms that the original user is indeed infected, then a stronger warning – effectively a red alert – will be sent instead, signalling that the other users should go into quarantine.

There’s been a lot of pushback on the idea of embedding contact tracing in your smartphone. At least some of this pushback seems based on faulty assumptions.

While this is not the actual Apple/Google API, this comic about COVID-19 contact tracing does a great job of laying out the mechanics. I think this is worth reading before you make any assumptions about contact tracing and privacy.