Over the past few years a number of advances have been made towards the development of a new type of optical sensor based on the activation and detection by optical means of resonant vibrations in simple mechanical devices. This paper describes three strands of technology—resonator sensing, optical fibre systems and silicon micromachining—the judicious interweaving of which underlies the most promising of these advances; it then presents a review of the published work to date and ends with a personal view of possible future developments.