There is long known fact that diode can be used in reverse mode to generate small current when placed on a light. Computer scientists at Columbia University thought that this phenomenon could be used for dual purpose – harvest energy and take images. They constructed 30×40 array of diode pixels on a PCB. When this array is placed in environment with more than 300 lux brightness it is capable to collect enough energy to power microcontroller and take a picture every second.
It seems pretty attractive perpetual photographing machine which would take images and power itself whenever there is a light. Collected power is stored in capacitor between image shoots. It is hard to tell what microcontroller is used here but it is definitely a low power (MSP430 could do the trick). They also calculated that 210×200 sensor grid could rise frame rate up to 30 images per second alternatively it could be equipped with low power wireless communication that could constantly send data to remote host.