Thanks to the development of automated, passive, sensor systems with algorithmic forms of processing and machine learning, a growing range of data has become relevant to processes of diagnosis and care. Google, for example, envisions that smart speakers will one day be able to diagnose the onset of Alzheimer’s before individuals or caregivers notice symptoms, and the same is true for a variety of illnesses and conditions ranging from the flu to depression. By the same token, researchers have scraped publicly available social media posts to search for patterns that correlate online behaviour with medical conditions. As tech companies move further into the health care sector, all kinds of data can do double duty as health data in ways that may have important benefits, but also raise issues of privacy and data protection.