Yesterday, Bryson Meunier spotted a new test in Google's mobile search results where they label smartphone-optimized pages with a little smartphone icon in the search results. Here posted some low quality images but Yoshihiko Yoshida has some better quality images which I am sharing here:
Google confirmed this test telling me:
We’re experimenting with ways to optimize the mobile search experience, including helping users identify smartphone-optimized sites. We don’t have any more details to share at the moment, but thank you for checking in.
Since Google offered up their official recommendation on mobile SEO, this is a good indicator (if you see the test) to see if your site is indeed implemented properly for Google to recognize that your site is smartphone optimized or not. There is no such feature in Google Webmaster Tools as far as I know. There are mobile sitemaps, but that is used for feature phones.
I am also pretty sure Google had a similar implementation, of labeling phone friendly pages in the search results, specifically for feature phones. Moving it to smartphones is neat, although I am not sure if Google will add this clutter to the page or not in the future?