1. A system, comprising: a smart ring configured to be worn on a first segment of a finger of a user; at least one flexion sensor secured to the smart ring in a manner that can detect a distance between the at least one flexion sensor and a second segment of the finger; and, an input component configured to: analyze signals from the at least one flexion sensor to detect an initialization sequence, in response to the detected initialization sequence, calibrate a coordinate system of the smart ring, and use the calibrated coordinate system to interpret further signals from the at least one flexion sensor.