Abstract: An electro-mechanical transducer suitable for use in a cot or bed to detect body movements comprising a resiliently compressible assembly which emits noise while being compressed or expanded and a microphone for detecting the noise thus produced thereby to permit of the control of alarm or signal means.The device is particularly designed to give warning of cessation of breathing movements of infants while asleep with the objective of reducing the incidence of so called "cot deaths".