A crash course in changing the world.
The interchangeable batteries could be installed into a Heel of a Shoe. Ideally one that has also been custom sized for the individual to make sure they have great foot health for the remainder of their life, thus keeping them mobile and this principle working better. Iphones are almost at the stage of being a mobile laptop. This is great they are for people on the go, which is ... Everyone these days! So whilst simultaneously encouraging an active and healthy lifestyle, benefiting health in general, we are thus able to prolong these effects even when technology is still in need of power without infringement on our personal being i.e. a small solar shield on a bag or hand held device that is separate and has to be carried around either in said bag, or in a pocket which could be really annoying for example one is out hiking in the Scotland Highlands for arguments sake.
As the individual walks, runs or jogs - the energy transmutation takes place in ideally a range of methods as described earlier. The installation would be limited at first to select shoes, but as technology improves the would hopefully become a standard in all footwear, allow other uses e.g. universal battery for the home to bring home the bacon and some free energy, all in a days work! Heck even the kids can chip in! Better still if lost in the middle of no-where with a dead batter a quick exchange in the Iphone battery in this particular example and boom! Back to power on and hopefully full signal to phone for help or perhaps just a pizza!
The aim would be to not only design this fit all shoes (Except high heels *sigh* and pumps) but also subtly hide within so that nothing is noticed, the actual person is insulated from electrical shocks and it is capable of easier repair e.g. simply unplug the wh*** unit out.
In this hiking boot for example the heel has ample space and part of the cushioning provide by the current materials could for example convert pressure on the heel by perhaps powering an small internal dynamo or electronic gel that rubs against a surface to generate heat and static which is then converted immediately into electricity. The biggest issue would be water proofing the shoes in order to protect the equipment and the individuals, but heck I'm sure some scientist could enhance other clothing to match this concept or better still combine multiple threads and enhance human generated electrify proportionately to their output.
Imagine having a matching set with these gloves:
The eventual aim of this humble technology would be one of these for every person to use for their day to day living, you know shopping hiking, etc ...
Conversely the flying may actually reduce health buy lack of actually walking, but man how much fun could you have! ^_^