1. A portable eye tracker device comprising: a frame adapted for wearing by a user; at least one optics holding member, wherein the optics holding member comprises: at least one illuminator configured to selectively illuminate at least a portion of at least one eye of the user; and at least one image sensor configured to capture image data representing images of at least a portion of at least one eye of the user; and a control unit configured to: control the at least one illuminator for the selective illumination of at least a portion of at least one eye of the user; receive the image data from the at least one image sensor; and calibrate at least one illuminator, at least one image sensor, or an algorithm of the control unit.