Dana Ross

Widget that displays on your WordPress search results page with similar items from your Flickr, YouTube, and Twitter feeds.
For example, someone searching for “cat” on your site might see Flickr photos you’ve tagged with “cat”, or that funny YouTube video you took of your kitty the other day.
Currently searches: * Flickr * Twitter * YouTube
…or any combination of the above!
View the announcement for this plugin at http://www.slideshare.net/fvcp/wpexternalsearch

Dave’s External Search

Widget that displays on your WordPress search results page with similar items from your Flickr, YouTube, and Twitter feeds.

jmarreros

This Plugin allows to use an external image as Featured Image, this can be especially useful if you house your images in another location.
This Plugin is compatible with Nelio External Featured Image Metadata, so you can reuse your data in case you want to uninstall Nelio Plugin.

External URL Featured Image

It is what I was looking for: simplicity.

$external_image = get_post_meta( $post->ID, '_dcms_eufi_img', true );

Works well for me

Use an external url image as Featured Image for your posts, pages, and other kind of post types.

Dave’s External Search vs External URL Featured Image