Free idea -- Self-winding phone
As there is self-winding watches, or chronographs as the enthusiasts calls them, is a technique where movement is captured to spin a flywheel that translates the movement into stored energy, energy that is used to keep the watch/chronograph running without the need to manually wind it every once in a while.
Imagine a variant of this that would live inside a phone, where much of the mechanics could do the same work, but instead of winding up a spring in a clockwork, would drive a small generator that generates electricity that would charge a battery in a phone.
A phone is usually worn or carried by a person, creating movement. If this movement is captured and turned into an electrical charge it would make the intervals between charging a phone through mains electrical network less often.
As we're also moving fast towards the future, there is most probably also a MEMS (micro-electromechanical system) variant of this that could be developed as well. Imagine having every vibration translated into electrical charge.
Also, the word "phone" could probably be interchanged with any type of device in the category of "wear-ables".
I would not mind if my phone only required to be charged once a week. It could potentially also save lots of electricity as people leave their chargers plugged in all the time, even while not being used.
I would like to see technique like this being developed, just like Jonas Salk didn't patent the Polio vaccine, stuff like this should not be patented, as they would be good for the society and nobody in particular should alone benefit from such an idea.