Cardiovascular diseases and, in particular, diseases related to arrhythmias are a problem that affects a significant percentage of the population, being one of the major causes of death in Europe. New advances in the fields of PDAs, mobile phones, wireless communications and vital parameter sensors have permitted the development of revolutionary medical monitoring systems, which strikingly improve the lifestyle of patients. However, not all those monitoring systems provide patients with real assistance – anywhere and at any time. We have developed a system that goes a step further than the previous approaches, being designed to capture, record and, as a distinctive feature, locally analyze the ECG signals in a PDA carried by the patient. In that sense, the system has a decision support module based on decision tree methods that can detect, with high precision, any arrhythmias that the user may be suffering. Alarms can then be activated in time to alert a medical center in order to provide the proper medical assistance. One of our aims when building the system has been to optimize limited and expensive resources like PDA memory size and wireless communication costs. Moreover, accessibility is also an important feature of the system that has been achieved by the development of web services to query the data computed in the PDA. In this way, authorized personnel (physicians and relatives) can easily obtain access to that data.