I have been looking for a cost-effective lightweight backup strategy for travelling, which doesn't involve taking a laptop. I have looked at the Hyperdrive etc but they are expensive for what they do IMHO.
I purchased a Raspberry Pi which is a small £27.80 computer and I have successfully used the Pi to provide a lightweight but comprehensive backup solution using an existing 500Mb portable hard drive.
I am by no means a Raspberry Pi expert. I have collected the necessary steps from around the web and put them together in a user-friendly format, which I hope fellow photographers will find useful.