You would think that it would be obvious, but it is not: what is a biosensor? Biosensors have been defined by Intel anthropologist Dawn Nafus (2016a: xiii) as devices that ‘indicate something about the body or the physical environment’, and biosensing as a practice that ‘uses information technology to understand something about bodies or the environment in which they live, whether the technology is at the cutting edge or not’. Standing at the intersection of everyday experience, scientific, medical and technical knowledges, media-platform economies, transformations in the biopolitics of health care, and cultural-material imaginaries of digital health, it is hardly surprising that biosensors are lively assemblages. They increasingly form a stage – a platform – on which problems of childhood, puberty, sexualities, reproduction, wellness, fitness, disease, ageing, medical expertise, health-care provision, economic productivity and citizenship, among others, play out.

Questions teem around these broad, pragmatic definitions of biosensors and biosensing. Are biosensors really concerned with ‘the body’ or ‘the physical environment’, or are they an outgrowth of the fitness and health-lifestyle industries? (Given that things seem to get inside us, do bodies live in an environment anyway?) Do the ideas of ‘indicating’ and ‘understanding’ accommodate what people do with biosensors? What else do they do with them? Do biosensors and biosensing challenge or extend traditional medical authority? Does biosensing increase people's control over their health, as is often claimed? What is the connection between more data and health? Who is biosensing who? What is the relation between biosensing and people's anxiety about their health? How do people subvert or reinvent biosensors to assure themselves of health? How does biosensing participate in making certain forms of selfhood and group viable? What socio-material networks do biosensing practices produce and rely on? Who is profiting from biosensing and who is not, and how? What new forms of work and care are produced in biosensing? How does the dream of continuous monitoring animate biosensing? How might collectives or communities thrive through biosensing? What, if any, policy framework might meet public concerns about health biosensors?

In this book, we offer some ways of responding to this panoply of questions and perhaps framing some new ones.