I can't really possibly think of any benefit automatic commits could bring.
If I have some unfinished work on my local computer, I can either have two choices, or a single one depending on this factor:
Am I using distrubuted versioning or centralized versioning?
In the first scenario I can committ locally without pushing to the central repository, thus gaining the benefits of version control without forcing other people to deal with my unfinished or possibly broken code.
If it's centralized versioning, you suck it up and keep it locally for the next day, hoping your HDD doesn't fail overnight.
It's really simple as that. Then to just answer your question, no, I don't recall such functionality in vault (or any other versioning software) and I think that would be a terrible idea.