
Hydrogen fuel cells aren't exactly a new technology; they've been used to power Honda cars, for example, and they bring their own set of problems, especially in the context of smartphones or laptops.
But Apple might have a solution. One of the patent applications describes a "fuel cell system which is capable of both providing power to and receiving power from a rechargeable battery in a portable computing device. This eliminates the need for a bulky and heavy battery within the fuel cell system, which can significantly reduce the size, weight and cost of the fuel cell system."