It's a great question and as the article Andy mentioned points out, there are benefits to optimizing your titles and metas for mobile. However if the site is responsive, then there is only one page and therefore only one title and description. If you serve different versions then you can do it. You'd need to host the mobile version on something like m.example.com or do what Google calls "Dynamically Serving Different HTML On The Same URL". You can learn more here: https://developers.google.com/webmasters/smartphone-sites/details.
-M