This is a prototype showing the iPhone 6s powered by hydrogen fuel cell battery. Intelligent Energy shows the capabilities for the iPhone 6s to use up to seven days base on regular usage. The hydrogen requires an oxygen for it to react and produce energy. That is why there are holes behind the iPhone.
They also showcased the same concept on a Macbook Air. Although it is not ready for production yet, the new hydrogen fuel cell opens up possibilities to extends current battery life or they could squeeze down current battery size for the same amount of battery capacity.