A method of processing heart rate data to convert biometric data to meaningful heath risk indications comprises: a processor processing heart rate data, obtained from a user by a sensor device over a monitoring period of at least one day, in dependence on biometric data for the user, to determine an aggregate heartbeat value for the user over said monitoring period a processor determining a health-predictive activity score from said aggregate heartbeat value according to a model calibrated with peak oxygen uptake of population study subjects and a user device providing a risk indicator derived by linear scaling of said health-predictive activity score to the user by means of a user interface.
