1. A wireless sensor device for automated sleep staging, the wireless sensor device comprising: a sensor to determine at least one physiological signal; a processor coupled to the sensor; and a memory device coupled to the processor, wherein the memory device includes an application that, when executed by the processor, causes the processor to: extract at least one feature from each of a plurality of epochs of the at least one physiological signal; scale the at least one feature for each epoch; determine a feature vector for each epoch using the at least one scaled feature; and classify each epoch into one of a plurality of sleep stages by inputting each feature vector into a machine learning classifier unit, wherein the at least one scaled feature enables the machine learning classifier unit to classify epochs with features of varying magnitudes.