Future iPhones and iPads could be powered by external hydrogen fuel cells. Apple has been granted a patent (number 20150249280) by the U.S. Patent & Trademark Office for a "fuel cell system to power a portable computing device."
This fuel cell system includes a fuel cell stack that converts fuel into electrical power. It also includes a fuel source for the fuel cell stack and a controller that controls operation of the system.
The fuel system also includes an interface to the iOS device (though it could conceivably also work with Mac laptops). The interface would sport a communication link that provides bidirectional communication between the computing device and the controller for the fuel cell system.
One of Apple's reasons behind the patent filing is the company's environmental concerns. In the patent Apple says that "our country's continuing reliance on fossil fuels has forced our government to maintain complicated political and military relationships with unstable governments in the Middle East, and has also exposed our coastlines and our citizens to the associated hazards of offshore drilling." These problems have led to an increasing awareness and desire on the part of consumers to promote and use renewable energy sources.
For example, the Electronic Product Environmental Assessment Tool (EPEAT) is presently used to produce data that helps consumers evaluate the environmental friendliness of electronic products. What's more, the EPEAT score for an electronic product can be increased by providing a renewable energy source for the product.
Apple says that, as a consequence of this increased consumer awareness, electronics manufacturers have become "very interested" in developing renewable energy sources for their products, and they have been exploring a number of promising renewable energy sources such as hydrogen fuel cells. Hydrogen fuel cells have a number of advantages.
Apple says such fuel cells and associated fuels have the potential to enable continued operation of portable electronic devices for days or even weeks without refueling. However, it's extremely challenging to design hydrogen fuel cell systems which are sufficiently portable and cost-effective to be used with portable electronic devices.
Apple thinks it's up to the challenge. Keep in mind, though, that the company files LOTS of patents for inventions that never actually come to fruition.