1. Apparatus comprising: (a) a camera; (b) a projector for projecting images on a surface, which surface is separate from the apparatus and is not dedicated to electronic visual display; (c) a transceiver for connecting to a global network; and (d) a digital computer for (i) performing analysis of visual data captured by the camera (A) to identify a solid object or a feature of the solid object, neither the object nor the feature being an image projected by the projector, and (B) to recognize a gesture made by a human in the air while the human is neither in physical contact with, nor holding an object that is in physical contact with, a solid surface, and (ii) based at least in part on the analysis: outputting instructions to obtain, from the global network, information about the object or feature; receiving and processing data indicative of the information, and outputting instructions to make changes to the images, in a way that the changes depend at least in part on the information and the gesture; wherein (A) the global network comprises the Internet, the World-Wide Web, or any other global system of interconnected computer networks, and (B) the apparatus is wearable in a manner in which weight of the apparatus is not supported by a human user's hands.