A mouse having X- and Y-position encoders, and associated circuitry for generating X- and Y-movement data, additionally includes an optical sensor for producing grey-scale image data, thereby allowing the mouse to serve both as a positioning device and an optical input device. Desirably, the substrate on which the optical sensor is formed also includes a steganographic decoder. This decoder can enable a variety of functionality, such as linking to web addresses steganographically encoded in print media (e.g., by subtle inking variations or by texture). In other embodiments, such a peripheral is provided without mouse-like functionality, and again permits reading machine-readable indicia printed in catalogs and the like.