Device-based activity classification using predictive feature analysis is described, including receiving a signal from a sensor configured to measure a heart rate coupled to a device, the sensor being configured to sense the signal over a time period, evaluating the signal to generate data associated with the heart rate, the data being further evaluated to select a classifier, invoking the classifier, the classifier being configured to evaluate the data to identify a predictive feature, the predictive feature invoking an application configured to determine a state using a feature interpreter, the application also being configured to evaluate other data from another signal, the signal being configured to detect a respiration rate, and processing the data and the other data using the application and the feature interpreter to generate information associated with sleep, the information being configured to display on an interface associated with the device.