An apparatus includes a mounting portion and a sensor portion. The mounting portion is configured to fit over a nose of a preselected patient. The mounting portion includes a base and a pair of rigid nose pads fixedly coupled to the base. Each nose pad of the pair of nose pads includes a respective nose-gripping surface. The nose-gripping surfaces of the nose pads are configured to engage the nose of the preselected patient at respective predetermined locations along the nose. Each nose-gripping surface is sized and shaped to complement a corresponding unique structural feature of the nose of the preselected patient at the predetermined location. A sensor portion is fixedly attached to the mounting portion. The sensor portion includes a first sensor configured to generate a first signal corresponding to a position of the first sensor in three-dimensional space.