The possibility to monitor the cardio-respiratory activity in a non-invasive way, by measuring thoracic displacement using cost-effective microwave Doppler technology, has been studied. Several laboratory tests were performed in order to demonstrate the feasibility of the proposed electromagnetic measurement method. Time domain signal processing techniques have been used in order to evaluate the main frequency and rate variability of the heartbeat and respiration signals. They have shown a very good correlation coefficient with the electrocardiogram and spirometer results, used as reference instruments. On the other hand, a simple electromagnetic model was developed in order to analyze the scattering problem, using appropriate analytical and numerical techniques.