Spotted at phys.org is a story on a prototype video camera that is the first to be fully self-powered:
A leading researcher in computational imaging, Nayar realized that although digital cameras and solar panels have different purposes - one measures light while the other converts light to power - both are constructed from essentially the same components.
...
The pixel design is very simple, and uses just two transistors. During each image capture cycle, the pixels are used first to record and read out the image and then to harvest energy and charge the sensor's power supply—the image sensor continuously toggles between image capture and power harvesting modes.
Additional background at Columbia Engineering Computer Vision Lab
(Score: 2) by ikanreed on Wednesday April 15 2015, @09:12PM
Well, presumably if you were a really clever electrical with CIA/NSA funding, you could probably rig a larger circuit to turn on under some specific conditions without having too high an energy demand, and start recording to a tiny flash drive off a tiny battery.
A PV to recharge might be really visible, whereas a incredibly tiny self-powered camera might be easier to hide. And you can just leave it there, forever.