Adding “ ” before the last word in multiple defined areas with a plugin

How would this be done with javascript or a plugin? This would prevent widows from happening in my WordPress posts. Shaun Inman has created a similar plugin for post titles, but not for actual posts. Can his plugin be modified to include posts?

http://shauninman.com/archive/2006/08/22/widont_wordpress_plugin

Here is a screenshot of my post with a widow:

Screen Shot 2012-08-05 at 1.42.13 PM.png

Solutions Collecting From Web of "Adding “ ” before the last word in multiple defined areas with a plugin"