Breathing rate is an important sensitive marker of illness. Frequent measurements are needed to observe early trends that allow detoriation to be detected. Current automatic methods are not practical and poorly tolerated by sick patients. We have invented a small wireless sensor (CE marked) that is minimally intrusive. It is attached to the patient’s side to measure breathing movements and we have shown that it is accurate and reliable in surgical patients. We aim to validate its performance in the acutely ill, who are another important candidate group with varying patterns of breathing, very different from surgical patients.