How can I get ob_start() to work in a class within my WordPress Plugin?

Solution:

class Obstart 
{ 
      public static function callback($buffer)
      { 
           return $buffer; 
      } 

      public static function add_ob_start()
      { 
           global $buffer; 

           ob_start( self::callback($buffer) ); 
      }

      public static function flush_ob_end()
      { 
           ob_end_flush(); 
      } 
} 

add_action('init', array( 'Obstart', 'add_ob_start' ) ); 
add_action('wp_footer', array( 'Obstart', 'flush_ob_end' ) );