From Google Blog:
"We’re now testing a smart contact lens that’s built to measure glucose levels in tears using a tiny wireless chip and miniaturized glucose sensor that are embedded between two layers of soft contact lens material. We’re testing prototypes that can generate a reading once per second. We’re also investigating the potential for this to serve as an early warning for the wearer, so we’re exploring integrating tiny LED lights that could light up to indicate that glucose levels have crossed above or below certain thresholds. It’s still early days for this technology, but we’ve completed multiple clinical research studies which are helping to refine our prototype. We hope this could someday lead to a new way for people with diabetes to manage their disease."