Sony has patented a contact lens that can take videos of what you see.  Embedded sensors in the contact lens’ pick up on voluntary as opposed to involuntary blinks which trigger the video recording.  Image capture and storage will be embedded in the contact lens around the iris. Sensors will be able to convert eye movements into energy to power the lens.

The technology works in theory but is still a long way off from making it into something consumers can take advantage of.