I find it very relaxing to keep with me at all times the data I don't want to loose. While I work an external drive is plugged in and Time Machine keeps regular backups on a 100GB partition of it. However, although this drive is very small and light, I don't bring it everywhere. What I keep everywhere is an up-to-date copy of my work on a tiny 8GB USB key attached to my key-ring.
So whenever I leave after work I update the key, and this is how it gets done.
Mac OS X detects the new device and mounts it as it does normally. In addition the key is recognized, its contents are synchronized, and the key is ejected. This can be automated with the following steps.
Step 1: Download and install Rsyncx.
Step 2: Create this workflow with Automator.
Drag and drop Run Shell Script action. Copy and paste the following script in a single line. Replace [KeyName] and [FolderPath] with your values.
if mount | grep -qs '[KeyName]'; then time sudo rsync -s -e ssh "[FolderPath]" /Volumes/[KeyName]/; fi
Drag and drop Get Specified Finder Items action, click "Add...", type a slash and a box appears. In the box type /Volumes/[KeyName] .
Drag and drop Eject Disk action.
Step 3: Save the workflow as plugin for folder actions attached to folder /Volumes . Save it as a workflow as well if you want to modify it later.
Step 4: Enable folder actions at startup.
To deactivate the workflow and use the USB key normally, Ctrl-click on any item in Finder, moseover "More", click "Configure Folder Actions...". The workflow is associated to "Volumes". Uncheck it.