The six publications presented in this thesis represent a programme of research spanning six years (2014-2019). The papers investigate existing technological interventions for people with complex long-term neurodisabilities (LTNs) across the lifespan focusing on adults post stroke and children and young people (CAYP) with Attention Deficit Hyperactivity Disorder (ADHD). Individuals with complex LTNs spend minimal time with their clinicians compared to time away from them. Therefore, alternative complex interventions such as the use of technology are being used to facilitate the self-management of their condition. These are explored using primary (publications two, three and six) and secondary (publications one, four and six) research methods in the publications in this thesis. The overarching finding from the research undertaken and reported in papers one to five is that whilst a plethora of research has been undertaken in the context of health technology a failure to evaluate or develop these appropriately means that many technologies still remain unsuitable. Paper six in many ways is a methodological response to the limitations identified. In this research Realist Evaluation (RE) was uniquely adopted to design a set of recommendations for the future development of a technological self-management intervention for CAYP with ADHD. This method could inform future research in other areas. The overall recommendation resulting from this body of work is that future development of complex interventions should be iterative, involve end users and stakeholders at every stage of evolution. There is also a necessity to be transparent in the reporting of findings, ensuring that personal and environmental contexts are taken into consideration. The challenges facing individuals with long-term conditions are complex and cross-disciplinary research approaches which position end users as experts are required to ensure that technological responses are developed that are fit for purpose. The use of RE and co-design methodologies could help to achieve these recommendations.