The UK's Covid-19 contact tracing app is coming soon. Many countries and large tech companies are working on similar apps, or have already released them, and one of the key features of the UK version is that it sends data back to a central database hosted by the National Health Service. This approach has already attracted concerns from civil liberties and privacy advocates, raising concerns about how it might be used beyond contact tracing for infection. However if you dig a little into the details, it looks like a  good balance between the analytic benefits to be gained from creating a national movement and infection dataset, and minimising the risk of individual identification for other purposes.