That's because our own bodies just might be the sustainable energy sources of the near future, generating electricity from our own body heat, physical movement and vibrations.
Roger Highfield of the Science Museum Group writes that scientists are already at work on a number of such devices, with the first wave of human-powered generators hitting the market in the next two years.
The applications would range from personal health to entertainment. For example, pacemaker batteries must be replaced every few years. But a pacemaker running off a piezoelectric current could provide a permanent energy source, reducing the need for risky and expensive operations.
The word piezoelectricity means to generate energy from pressure and can be derived from a number of sources, including ceramics, crystals and even biological material, such as DNA and bone.
Researchers have spent years attempting to derive energy from nontraditional sources. For example, the East Japan Railway Company has experimented with using train gates to generate electricity as commuters pass through them.
And researchers at MIT have been working on creating a "crowd farm" that would generate electricity from human movement in public spaces.
University of Wisconsin-Madison associate professor Tom Krupenkin told Highfield that placing a salty liquid within the soles of shoes could generate enough electricity to power many of the devices used by millions of consumers around the world.
"This is more than sufficient to power such common devices as smartphones and tablets," he said. "We expect the first product prototype to be available in one to two years."
However, don't start planning to charge your Kindle with an after-dinner walk around the block just yet. Laurie Winkless of the U.K.'s National Physical Laboratory says that piezoelectric devices could prove to be more trouble than they are worth, unless used properly. For example, "thermoelectric" clothing may be able to draw energy from the body but could leave the wearer feeling uncomfortably cold. And those saltwater shoe batteries may prove to be painful for people walking long-distances.
Still, even skeptics like Winkless see a promising future around the corner for these alternative energy generators.
"Energy harvesting pots could mean that boiling your pasta charges your mobile phone," she said. "The vibrations of your washing machine could power wireless sensors—or your TV remote could be powered just by you pressing the buttons."