It is well-known that physical activities contribute to keep the people healthy. However, the modern life style impacts negatively on the amount of physical activity that we do during the day. Many times the people do not perform enough exercise because they are not aware of the amount of physical activity that they have done. In order to make the persons aware of this aspect of his life, this article presents a mobile application that monitors the amount of exercise they do every day and it informs properly to the user. The system, named AMOPA, allows caregivers or doctors monitoring particular patients, to access this information remotely in order to support the person being monitored. The system was evaluated using laboratory tests, and the results indicate a good performance and accuracy in the detection of the people physical activities. Moreover, the monitored process has a low impact on the energy consumption of the devices used to capture and process the information.