In the past few years we have seen the development of several new technologies for the continuous and non-invasive monitoring of physiological glucose, such as the GlucoWatch, glucose-sensing skin patches and approaches based on a glucose-sensing tattoo. One approach that differs from current thinking is based on the determination and monitoring of tear glucose, which is well known to track blood glucose with an approximate 30 min lag time, using disposable and colorless contact lenses. These contact lenses can be worn by diabetics who can colorimetrically see changes in their contact lens color or other fluorescence-based properties, giving an indication of tear and blood glucose levels.