What is the most reliable backup device for digital RAW files in the field W/OUT a laptop?

Answer 1

There are various devices designed to allow you to download digital pictures in the field - see, for example, those made by Epson at http://www.epson.co.uk/products/product_hub/home_photo_viewers.htm
However, you will be unable to see RAW files on these as they do not contain any conversion software, and I don't think there are any made by other manufacturers that do. They are also relatively expensive - certainly you would be able to get a cheap laptop for the same price, or very little more, and that would be far more reliable. The only other way is to buy sufficient memory cards and retain your pics on those until you return to your computer.