Google's smart contact lens prototype will monitor the glucose levels in tears. One of the biggest health problem today is Diabetes, and having a monitor that wouldn't require to prick your fingers to draw blood will be really helpful.
The prototype contact lens has sensor between two layers of lenses that measures the glucose levels in tears. There is a minute pinhole in the lens that let fluid to seep in and the glucose monitor will analyze the glucose levels in the tears.
It also have a small antenna, capacitor and controller, to transmit the data to a smartphone or any handheld monitor, where that data can be read and analyzed.