Google has been mentioning this for a long time, your website should be “Mobile Friendly”. Well on April 21 2015 if they are not they will most likely take a hit in ranking.
I have received several Alert from Google Webmaster Tools “Fix mobile usability issues found on http://www.websitename.com.
Check your Google Webmaster Tools for Alerts about your site, if your site is not in Google Webmaster Tools it might be time to add it.
Check Webmaster Tools and Check Your Email for Alerts!
They are doing this because Mobile Usage Grows every year. See the info-graphic below from SlickText.
How Can I Test if My Site is Mobile Friendly? Go To https://www.google.com/webmasters/tools/mobile-friendly/ Check the Results for Your Site!