engasm89

The plugin is easy to use and it has a simple, user-friendly interface. 
It is also highly configurable, so you can customize it to meet your specific needs. 
The WordPress External Link Redirection plugin is free. 
It can help you triple your income from your ads by showing people more ads when they visit external links inside your articles or pages

External Link Redirection

The WordPress External Link Redirection plugin allows you to manage your site's external links and forward people to a waiting page with ads to m …

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.

External Link Redirection vs External URL Featured Image