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 basic architecture and initial development steps of an m-Health monitoring system that will be used in order to monitor children with suspected cardiac arrhythmias. The proposed system will be based on sensor networks, in order to monitor a subject while being in a predefined area like his/her house; while a module based on PDAs and wearable ECG recorders will be used in order to extent the coverage outside the patient's house. The system will be based on a variable sampling rate to conserve power for the possible arrhythmia episode. The system design has been completed, the hardware specifications have been decided and currently the system is going through the development phase.