<p>This paper investigates the central role of agility and participation in the development of digital assistive technologies for people with cognitive impairments. Flexibility and an iterative approach enable adaptation to changing requirements and ensure the active involvement of all relevant stakeholders throughout the development process. The methodological approach presented here integrates participatory methods in order to consider the specific needs of the user group and their caregivers right from the start. The multi-phase development cycle—from joint ideation, through mockups and prototyping, to comprehensive evaluation—is illustrated in the context of the development of an augmented reality based museum app. People with cognitive impairments are included early and continuously in the design and testing phases, thereby improving both the acceptance and everyday usability of the solution. Special emphasis is placed on the use of visual aids and iterative feedback loops, which facilitate communication and enhance the quality of results. Despite the increased organizational effort, it is shown that appreciative communication and transparent processes are essential for promoting self-determination and daily participation within the target group.</p>