Adults with cognitive impairments lack the means to organise their daily life, plan their appointments, cope with fatigue, and manage their budget. They manifest interest in using new technologies to be part of society. Unfortunately, the applications offered on smart phones are often beyond their cognitive abilities. The goal of this study was to design a mobile cognitive assistant to enhance autonomy of people living with acquired traumatic brain injury. Participatory design methodologies guided this research by involving adults with cognitive impairments (CI) and their caregivers in the early stages of the design process. The population of the study is composed of four male adults who present cognitive impairments (three with head injury and one with stroke) and three caregivers. The first phase of this research was to design the Services Assistance Mobile and Intelligent (SAMI) application based on the needs expressed by the participants. During three focus groups, needs emerged concerning planning, health monitoring and money management and led to the implementation of assistive solutions on an Android mobile phone. During the second phase, the participants evaluated the mobile assistant SAMI at home for eight weeks. The results demonstrate that the participants were able to participate actively in the conception of SAMI and to use it successfully. People with CI showed a slight improvement in their life satisfaction. Due to the small number of participants, these promising results need to be confirmed by a larger-scale study.