Robin Phillips

This plugin was originally written for a client, but may be useful for others. It simply creates a discrete banner when viewed on mobile. This banner can include a link, to a mailing list for example.

Mobile Banner

Create a banner with a link at the bottom of the screen, when viewed on mobile only.

Adnan Shahid

Responsive preview tool for WordPress admin to switch between mobile, tablet, and desktop viewports inside the dashboard.
Key features 
* One-click viewport buttons (Mobile / Tablet / Desktop) 
* Uses an iframe to preview your site inside the WordPress admin 
* No tracking, no external requests, no background processes
<h3>License</h3>
GPLv2 or later.

Responsive Admin Viewports Preview

Responsive preview tool for WordPress admin to switch between mobile, tablet, and desktop viewports inside the dashboard.

Mobile Banner vs Responsive Admin Viewports Preview