Biometric identification is now closely integrated with other forms of data, data systems and communications technologies, such as smartphones, metadata and social media, and as the key security feature on smartphones, and by extension, social media accounts, online profiles and identity. For this reason, we consider the interaction between biometric and other forms of identification data, and data systems, building upon the consideration of the main biometrics in the first three chapters. We begin with a general discussion of data systems and integration. This is followed by a discussion of the interrelationship with biometrics, and broader significance of, metadata, smartphone applications and social media. In combination with biometric identification technologies, these provide detailed insights into individuals’ activities and behaviours. The ethical analysis in this chapter focuses on dual use dilemmas. Roughly speaking, dual use dilemmas in science and technology arise in virtue of the fact that such science and technology can be used to greatly benefit humankind, but also, unfortunately, to cause great harm to humankind. Consider, for instance, nuclear science and technology. It can be used as a cheap and peaceful energy source, or to build nuclear weapons. Similarly, facial recognition technology could be used by police only to track persons guilty of serious crimes; or it could be used to monitor ordinary citizens’ behaviour by an authoritarian government.