Google has made a change to how Skip Redirect on smartphone SERPs works, so it now also uses the rel-alternate-media annotations recommended in Google's guidelines on separate mobile URLs.
Skip Redirect is when Google changes the link target it shows in smartphone results if it knows the URL it's showing redirects users to a different smartphone-optimized page.
"In this case, even if the desktop page doesn't automatically redirect to the smartphone page, if we discover valid annotations linking the desktop and smartphone pages, our algorithms may still change the link target shown in the search results to point directly to the smartphone page," Google's Pierre Far says in a Google+ post. "I know many webmasters asked me about this exact thing, and now you can be happy."
"Skip redirect changed only the URL in the HTML, i.e., the click URL, and didn't change the URL that was displayed," he notes. "The rel-alternate-media annotations change both, i.e. we display and link directly to the smartphone URL."
The Skip Redirect feature was introduced in late 2011. More on this and smartphone Googlebot-mobile in a blog post from the Webmaster Central blog.[via Search Engine Roundtable]