Scientists at Singapore's Institute of Bioengieering and Nanotechnology have developed contact lenses that deliver eye medication to treat diseases like glaucoma. From New Scientist:
"If the drug is water-soluble, it will be trapped within a network of tiny inter-connected, water-filled channels in the material. If it's water-insoluble, it will be trapped within nano-spaces in the polymer matrix, and slowly leach out into the channels. In contact with fluid on the eyeball, these channels open up and release the drug."