Boy, it would be nice to have a program that automatically backs up a specified list of files every time I perform an edit on them.
So for instance, if I had a couple of txt files in my documents that I frequently edit, this hypothetical program would run in the background, constantly checking for the "modified date" of these files, and every time this date changes, it would create a new backup in "my documents/backups/". So for example, after a while of using this program I would have dozens of files like "todo_1433_15-02-2006.txt" in this backup folder.
This is not much different than "incremental saves" that some programs feature, or history pages of wikis. I really believe it would become handy to many.