<p>An infant monitoring system includes a transmitter unit having a waterproof housing (6), with means for attaching the housing to the infant. An acoustic heart sound detector (11) is contained within the housing to convert heart sounds into electrical signals. A DSP unit (12) processes the output signals to distinguish the heart beats from background noise and generates a warning state if the monitored heart rate falls below a predetermined safe range. A battery-powered transmitter (14) generates radio signals which distinguish between a normal quiescent state and the warning state signalled by the processing unit (12), to activate an alarm in a remote receiver unit. A temperature sensor (41) may also be included to raise an alarm if the infants body temperature rises to a dangerous level.</p>
