The development of efficient mechanisms for detecting health issues in patients as early as possible is very welcome since the probability of positive outcomes from treatments increases if the health problem is detected on its early stages. On the other hand, many health issues can even be avoided if the condition of risk is detected before the patient start suffering from the disease. In this work, we propose a novel, efficient and low cost solution for indoor monitoring of patients for medical purposes based on Wi-Fi signal strength intensities and mobile computing. The output of our solution consist of reports containing the patterns of room occupation by patients inside home. These reports will allow health care professionals to detect changes on the behavior of patients that can be interpreted as early signs of health related issues. The proposed solution was implemented in an Android smartphone and tested in a real scenario. To assess our solution, 10 monitoring periods with the duration of approximately one hour each, were performed at different times. During each monitoring period, 40 random points were selected as measuring points and 391 correct detections out of 400 possible were reached, corresponding to an average effectiveness of 97.75%.138 26682673