What would you recommend to use as far as manipulating the admin bar goes? I was thinking to just add a new admin bar node, and with CSS set a background image for the icon. Then in the node, just output the count.

I have no idea how to add bubble notifications on the admin menus or admin submenus though. Any advice?
You just create the bubble (circle) with CSS, and have text site on top of it.
Example CSS
span.mbe-update-bubble{
position: absolute !important;
top: 6px !important;
left: 6px !important;
-webkit-border-radius: 10px !important;
-khtml-border-radius: 10px !important;
-moz-border-radius: 10px !important;
border-radius: 10px !important;
background: #ccc !important;
color: #464646 !important;
width: 10px !important;
height: 10px !important;
padding: 3px !important;
font-size: 11px !important;
line-height: 10px !important;
display: inline-block !important;
text-align: center !important;
text-shadow: none !important;
font-weight: bold !important;
}
span.mbe-ab-text{
position: relative !important;
margin: 0px -6px !important;
font-weight: normal !important;
}
span.mbe-ab-text-active{
position: relative !important;
margin-left: 14px !important;
color: #91b1c6 !important;
font-weight: bold !important;
text-shadow: 0px 0px 1px #000 !important;
}
Adding a pending posts function:
function admin_tool_bar($wp_admin_bar){
global $wp_admin_bar;
$post_type="testimonial";
$count = wp_count_posts($post_type);
$args = array(
'id' => 'mbe_testimonials_pending',
'href' => admin_url('/edit.php?post_status=pending&post_type=".$post_type, "http'),
'parent' => 'top-secondary'
);
if($count->pending == 1){
$title=" Testimonial Awaiting Moderation";
} else{
$title=" Testimonials Awaiting Moderation";
}
$args['meta']['title'] = $title;
if($count->pending == 0){
$display = '<span class="mbe-ab-text">'.$count->pending.' '.$title.'</span>';
} else{
$display = '<span class="mbe-update-bubble">'.$count->pending.'</span><span class="mbe-ab-text-active">'.$title.'</span>';
}
$args['title'] = $display;
$wp_admin_bar->add_node($args);
}
And in order for the admin bar item to be added, fire the hook:
add_action('wp_before_admin_bar_render', 'admin_tool_bar', 999);
Example Screenshot:
