Google and Apple Know

They know if you’re sleeping. They know if you’re awake. Bad or good, not so much — but they know if you’ve been out of your house. At least if you’ve taking your phone with you. If you have, then they know if you’ve been close to others. Can they know this without knowing who you are?
Yes.
Would you opt in to a service that would alert you if you’ve been close to others who have contracted Corona virus?
Maybe.
Would we freak out a little if we knew how much data they have, even if it is anonymous and private?
Yes. Of course.
The only real issue is them being open about how much data they have. This could help us all. We probably need to sideline the yuck factor as they already have this data.