The bluetooth contact tracing discussion is all over the news now.
There's this project, which is being sold as doing the right thing regarding privacy: https://www.pepp-pt.org/
Unfortunately they don't seem to intend releasing anything as free software :(
> We are establishing a partner management team to help you get going quickly.
> As a partner, you will: … have access to our documentation and the source code of a reference implementation.
This is a tiny, friendly fedi server!