Figured this out with Ben's help (who I believe is the creator of the excellent Fishpig extension).
I created a custom post (with the Custom Post Type UI plugin for WP) and a custom field (with the Advanced Custom Fields plugin for WP).
On my Homepage in the CMS I added in the content area
{{block type="wordpress/sidebar_widget_posts" name="wordpress.widget.recent_posts" post_count="5" post_type="slider_home" template="wordpress/sidebar/widget/slider_home.phtml"}}
In that block, slider_home is my post type and slider_home.phtml is a new file I created that pulls the code from wordpress/sidebar/widget/posts.phtml but customizes it to my need.
Within the loop in slider_home.phtml I took out what was currently there and added:
<?php $image = $post->getMetaValue('image'); ?>
<?php $url = $post->getMetaValue('url'); ?>
<a href="<?php echo $url; ?>" target="_blank">
<img src="<?php echo $image; ?>" />
</a>
which is pulling in the custom fields I made in Wordpress. works perfectly and now my client will be able to update their Magento site through the Wordpress CMS.