People with intellectual disability or psychiatric disorders and cognitive dysfunctions may need assistive technology to maintain and improve their levels of functioning and independence. This study assessed a smartphone-based system to remind the user to initiate functional daily activities (e.g., setting a table for lunch) and perform them without the support of a caregiver. The system was evaluated through a non-concurrent multiple baseline design across two groups of participants. During the intervention sessions, the participants were provided with a system involving a Samsung Galaxy A3 smartphone fitted with the Easy Alarm YouTube application and audio files. The alarm served to remind the participant to carry out a planned activity. Following the reminder, the smartphone presented each of the step instructions preset for the activity. The data showed a statistically significant increase in the number of activities initiated independently from baseline to intervention for all participants. All participants also showed a significant increase in the number of activity steps correctly performed when supported by the smartphone. These results suggest that a low-cost system (i.e., smartphone) can be used to improve independence of people with intellectual disability or psychiatric disorders with cognitive dysfunctions.