Advances in wireless communications and networking technologies as well as computer and medical technologies, enable the development of small size, power efficient and more reliable medical multi-parameter recording systems, which can be used for continuous monitoring of patients. Through this paper we present the design and development of an m-health system platform that will be used in order to monitor children with suspected cardiac arrhythmias. The proposed system is based on sensor networks, in order to monitor a subject while being in a predefined area like his/her house; while another module based on PDAs and wearable ECG recorders will be used in order to extent the coverage outside the patient’s house. Furthermore the system will be based on a variable sampling rate to conserve power for the possible arrhythmia episode. The system design and development has been completed and currently is going through the initial testing phase for the first improvements.