Maxaud

This plugin allows you to define different CSS rules that get loaded into the page’s for specific devices.
Includes checks for 18 different tablet options and 13 different phone options.
This can be useful if you need to target specific phones or tablets to make CSS changes or show certain advertisements for certain devices.
For more options or if you feel like donating, check out the <a href="http://codecanyon.net/item/mobile-css-pro/3182318/" title="Mobile CSS Pro" rel="nofollow ugc">PRO version of Mobile CSS</a> that is available for purchase.

Mobile CSS

Allows you to define different CSS styles that get loaded for specific mobile devices.

Kevin

A wordpress plugin tool to test if a website uses responsive design and how it looks on different screen sizes, like smartphones, tablets, laptops and monitor. It’s easy to use you just use the shortcode with the url from the website you want to show the responsiveness from and that’s it ! EasyPeasy, Enjoy! You can test the responsive check plugin tool at this link : http://www.kdewindt.com/responsive-check/

Responsive Check

Just a Responsive check tool. You can check the responsiveness of every website with this tool by just entering the url in shortcode.

Mobile CSS vs Responsive Check