Sony's twirl N' take camera, by the use of spinning or dragging motion of the green wheel generates power for the camera.  There's no use for batteries and less damage to the earth.  All it takes is 15 seconds of the spin wheel to generate enough power for one shot.  It is still a bit primitive but it makes a great solution to the problems of batteries.

I'm guilty of turning on a light or fan and forgetting about it.  The most common one is the walk-in closet where often I grab the clothes needed and forget to come back to shut it off. That could easily cost 2 $ a month in wasted electricity.  This is a great idea that I would love to have in my whole house and makes complete sense.  We can save money and the resourses that we use to make it.