Add-on for Edit Flow that let's you set a "Reviewer" usergroups for individual users. All notifications related to that user go their assigned usergroup.

edit-flow_reviewer-add-on.php

<?php
/*
Plugin Name: Edit Flow - Reviewer Add-on
Plugin URI: http://editflow.wordpress.com
Description: An add-on for Edit Flow that allows you to assign review groups for users that will be notified any time a user updates a post.
Author: Mohammad Jangda
Version: 0.1
Author URI: http://www.digitalize.ca

Copyright 2009-2010 Mohammad Jangda

GNU General Public License, Free Software Foundation <http://creativecommons.org/licenses/GPL/2.0/>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

*/

define( 'EF_R_REVIEWER_METAKEY', 'ef_r_reviewer' );

function ef_r_admin_init( ) {
	global $edit_flow;
	
	if( !isset($edit_flow) )
		return;
	
	// Action to add dropdown to user profile
	add_action('show_user_profile', 'ef_r_select_reviewer');
	add_action('edit_user_profile', 'ef_r_select_reviewer');
	
	// action to save reviewer group to user profile
	add_action('user_profile_update_errors', 'ef_r_save_reviewer', 10, 3);
	
	// Filter the recipient list
	add_filter('ef_notification_recipients', 'ef_r_filter_recipients', 10, 2);
}

/**
 * Adds stuff to the user profile page to allow adding usergroup selecting options
 */
function ef_r_select_reviewer( ) {
	global $user_id, $profileuser;
	
	if( !$user_id ) return;
	
	// Only enable editing if user has the proper cap
	if( current_user_can('edit_usergroups') ) {
		// Assemble all necessary data
		$usergroups = ef_get_usergroups();
		$reviewer = ef_r_get_reviewer($user_id);
		
		if( !empty( $usergroups ) ) {
			$review_select = '<select name="'. EF_R_REVIEWER_METAKEY .'">';
			$review_select .= '<option value="">'. __('Not Assigned', 'edit-flow-reviewer') .'</option>';
			foreach( $usergroups as $usergroup ) {
				$selected = ( $reviewer == $usergroup->slug ) ? ' selected="selected"' : '';
			
				$review_select .= '<option value="'. $usergroup->slug .'"'. $selected .'>';
				$review_select .= $usergroup->name;
				$review_select .= '</option>';
			}
			$review_select .= '</select>';
		}
		
		?>
		<table class="form-table">
			<tbody>
				<tr>
					<th>
						<h3><?php _e('Review Group', 'edit-flow') ?></h3> 
						<p>
							<?php _e('Select the usergroup responsible for reviewing this user\'s post. Memebers of the selected usergroups will be included in all post update notifications', 'edit-flow-reviewer') ?><br />
						</p>
					</th>
					<td>
						<?php echo $review_select ?>
					</td>
				</tr>
			</tbody>
		</table>
		
		<?php 
	}

}

/**
 * Function called when a user's profile is updated
 * Adds user to specified usergroups
 * @param
 * @param
 * @param
 * @return
 */
function ef_r_save_reviewer( $errors, $update, $user ) {	
	
	if($update) {
		
		$user_id = $user->ID;
		
		if ( !current_user_can('edit_user', $user_id) )
			wp_die(__('Hey now, you don\'t have permission to edit this user.', 'edit-flow-reviewer'));
		
		if ( current_user_can( 'edit_usergroups' ) ) {
			
			// Get the POSTed reviewer data
			$reviewer = sanitize_text_field($_POST[EF_R_REVIEWER_METAKEY]);
			
			// Save the data!
			update_metadata( 'user', $user_id, EF_R_REVIEWER_METAKEY, $reviewer, false );
		}
	}
	return array( &$errors, $update, &$user );
}

function ef_r_get_reviewer( $user_id ) {
	
	if( !$user_id ) return false;
	
	$reviewer = get_metadata('user', $user_id, EF_R_REVIEWER_METAKEY, true);
	
	if( !$reviewer || is_wp_error($reviewer) )
		$reviewer = false;
	
	return $reviewer;
}

function ef_r_filter_recipients( $recipients, $post ) {
	
	$user_id = $post->post_author;
	if( !$user_id ) return array();
	
	$reviewer = ef_r_get_reviewer( $user_id );
	if( $reviewer )
		$reviewer_emails = ef_get_users_by_usermeta( EDIT_FLOW_USERGROUPS_USERMETA, $reviewer, 'user_email' );
	
	if( !$reviewer_emails )
		$reviewer_emails = array();
	
	$recipients = array_merge($recipients, $reviewer_emails);
	/*
	echo '<p>Before:</p>';
	print_r($recipients);
	
	echo '<p>After:</p>';
	print_r($reviewer_emails);
	
	die();
	*/
	return $recipients;
}

// Core hook to initialize the plugin
add_action('admin_init', 'ef_r_admin_init');