Some time later it dawned on me that these were basically step up converters, 3V to 5V!
So I turned this
|As it comes ..|
|Emergency charger with USB cable added|
You can prise apart the body of the charger (there are clips inside that will release, with some teasing) and remove the 3.5mm socket from the circuit board inside the top silver part then the hole left was just the right size for the USB socket and lead I had lying around from another project or you could use a power tip for the other supply connecter for the Arduino.
|Remove 3.5mm Socket (right) and add cable (left)|
You could also remove the small circuit board and use it with another battery holder or even inside your final design.
Due to the higher mAH rating of the AA batteires I think they will last a lot longer than a PP3 9V battery.