This is not a new plugin but version 3.0 is a totally rewrite of the old.
Link: http://wangenweb.com/wordpreciousss/
WordPreciousss extends the theme functionality in WordPress and actually creates a theme framework on your site - having a global set of templates, so all themes can basicly be CSS only if you like.
WordPreciousss also gives you the opportunity to add template files to Child Themes, so you're not limited to using only style.css and functions.php.
(As a sidenote; WordPreciousss was original created as Theme but remade into a plugin around in January this year to extend it's functionality even more)