Putting the pieces togetherUsing the USB hub means you can plug in the card reader and a memory stick (or a USB hard disk) at the same time - they all connected together and plugged in to the tablet as illustrated here:
Note that, if you're using a USB hard disk you'll probably need a powered USB hub unless the hard disk has its own power supply.
Once Nexus Media Importer in installed, when you connect a mass storage device you get a popup message asking if you want to open the app:
After you select OK and the app opens you'll be prompted to select the storage device you want to import from:
This is fine if you want to copy your photos onto the devices internal storage but we want to copy from one external storage (the SDHC card) onto another external device (the USB pen drive) and to do that we switch into the app's "Advanced" mode by selecting it in the drop down on the right that currently says "Importer".
Here we select our source and destination respectively and the app then switches to a view showing you the source file system on the left and the destination on the right.
Navigating to the correct folder is somewhat counter-intuitive at first as you have to tap the folder name to go into that folder, tapping on the folder icon to its left selects the folder meaning you can copy entire folders quite easily.
Once you've found the right folder e.g. the folder your camera saves photos to on the left and the place you're backing up those photos to on the right the app has a great feature allowing you to select any new photos and only copy those.
Once you've made a selection the other options such as "Copy" and "Move" become available in the menu and you pick the one you want.
Selecting one and you'll get a prompt about the action you're about to perform - hit OK and the transfer begins. The file transfer goes on in the background meaning you can swap to a different app while the transfer is happening or even put the tablet into standby to save power.
Assuming the read and write speeds of the memory cards and memory sticks you're using is good the transfers shouldn't take too long - the Transcend SDHC cards we bought had 90MB/s read speeds which made backup nice and quick.
We made two backups of our photos onto the two USB sticks, my wife kept one and I kept the other and then we just formatted and reused our SDHC cards as required. All in all, was a fairly low cost and space and weight efficient solution I was really happy with and will be using on subsequent trips.