Listen for change of class in jquery

Question

Is there a way in jquery to listen for a change to a node's class and then take some action on it if the class changes to a specific class? Specifically, I'm using the jquery tools tabs plugin with the slideshow and as the slideshow is playing, I need to be able to detect when the focus is on a particular tab/anchor so that I can unhide a specific div.

In my specific example, I need to know when:

<li><a class="nav-video" id="nav-video-video7" href="#video7-video">Video Link 7</a></li>

changes to the following with the class "current" added:

<li><a class="nav-video" id="nav-video-video7 current" href="#video7-video">Video Link 7</a></li>

Then I want to unhide a div at that moment.

Thanks!