Researchers at the University of Michigan have developed a prototype of an implantable eye pressure monitor for glaucoma patients that is believed to contain the first complete millimeter-scale computing system.

The entire device (which is only expected to become commercially available in several years) is just over 1 cubic millimeter. Yet,this tiny space contains an ultra low-power microprocessor, a pressure sensor, memory, a thin-film battery, a solar cell and a wireless radio with an antenna that can transmit data to an external reader device that would be held near the eye.

Read more ^[1] about the device on the University of Michigan website.