1. A method comprising, by one or more computing devices: accessing one or more data streams from a plurality of sensors, the sensors comprising a mood sensor and one or more of a heart-rate monitor, a blood-pressure monitor, a pulse oximeter, or an accelerometer, wherein: the data streams comprise mood data of a person from the mood sensor and one or more of heart-rate data of the person from the heart-rate monitor, blood-pressure data of the person from the blood-pressure monitor, pulse-oximetry data of the person from the pulse oximeter, or accelerometer data of the person from the accelerometer; a first data set from the data streams was collected from the person at a first time, the person being substantially stressed at the first time; and a second data set from the data streams was collected from the person at a second time, the person being substantially unstressed at the second time; analyzing the first data set and second data set with respect to each other; determining a current stress index of the person based on the analysis of the first data set and second data set with respect to each other.