Purpose – This paper aims to present an overview of the various ethical, societal and critical issues that micro- and nanotechnology-based small, energy self-sufficient sensor systems raise in different selected application fields. An ethical approach on the development of these technologies was taken in a very large international, multitechnological European project. The authors approach and methodology are presented in the paper and, based on this review, the authors propose general principles for this kind of work. Design/methodology/approach – The authors’ approach (...) is based on a great amount of experience working together in multi-disciplinary teams. Ethical issues have usually been handled in the authors’ work to some degree. In this project, the authors had the opportunity to emphasise the human view in technological development, utilise the authors’ experience from previous work and customise the authors’ approach to this particular case. In short, the authors created a wide set of application scenarios with technical and application field experts in the authors’ research project. The scenarios were evaluated with external application field experts, potential consumer users and ethics experts. Findings – Based on the authors’ experiences in this project and in previous work, the authors suggest a preliminary model for construction activity within technology development projects. The authors call this model the Human-Driven Design approach, and Ethics by Design as a more focussed sub-set of this approach. As all enabling technologies have both positive and negative usage possibilities, and so-called ethical assessment tends to focus on negative consequences, there are doubts from some stakeholders about including ethical perspectives in a technology development project. Research limitations/implications – The authors argue that the ethical perspective would be more influential if it were to provide a more positive and constructive contribution to the development of technology. The main findings related to the ethical challenges based on the actual work done in this project were the following: the main user concerns were in relation to access to information, digital division and the necessity of all the proposed measurements; the ethics experts highlighted the main ethical issues as privacy, autonomy, user control, freedom, medicalisation and human existence. Practical implications – Various technology assessment models and ethical approaches for technological development have been developed and performed for a long time, and recently, a new approach called Responsible Research and Innovation has been introduced. The authors’ intention is to give a concrete example for further development as a part of the development of this approach. Social implications – The authors’ study in this particular case covers various consumer application possibilities for small sensor systems. The application fields studied include health, well-being, safety, sustainability and empathic user interfaces. The authors believe that the ethical challenges identified are valuable to other researchers and practitioners who are studying and developing sensor-based solutions in similar fields. Originality/value – The authors’ study covers various consumer application possibilities of small sensor systems. The studied application fields include health, well-being, safety, sustainability and empathic user interfaces. The findings are valuable to other researchers and practitioners who are studying and developing sensor-based solutions to similar fields. (shrink)