You can add to your nav menu by setting
'lavaLamp' as value for the class parameter when calling wp_nav_menu in your (header) template file.
You'll probably have to uncheck the "use WP internal js" option and force to load the scripts shipped with this plugin.
(if you're running Fancybox, simply overwrite the easing js)
smarter script dequeue and enqueue functions will be implemented in a future release