SanDisk has just released its Backup USB which it claims is the first USB dongle with one-button backup.

SanDisk Ultra Backup and its 64GB USB is designed to collect and protect photos, music, video, and any type of personal files. There is no software all you have to do is push a button on the USB and the files are saved. 

Of course if you have more than 64 GB on your hard drive you are toast, but otherwise it is a pretty good idea. The disk is protected with a password and AES encryption. This is in case you lose it which with something that small is easy.

More here.