With the increase in size of the iPhone 6, phones are undoubtedly getting larger, so much so that an additional battery case may be too big to fit in your pocket.
Tylt has this covered with the Energi Sliding Power case for the iPhone 6 . It provides a 3200 mAh battery sleeve with a lightning a connector, that slides on and off the protective dual layered case. This allows you to use the two as one unit when charging on the go, whilst still being able to use your iPhone freely with just the case, when your phone has enough juice.
Battery: 3200mAh Lithium Polymer