A Java peon that goes off into the background to perform any menial tasks you care to throw at it.
Write reusable task classes for any tasks that you want to run in the background rather than lock up your UI. Use the task events fired on the UI event thread to update the UI to show the progress of the background tasks. Use annotations to define task concurrency rules. Necessary? No. Simple and useful? Hopefully!
See the wiki at https://github.com/githubpeon/peon/wiki for a more in depth overview and some examples.