The new International Targeting report is designed to help webmasters who have international sites and use lang markup understand common mistakes and learn what errors they need to fix, in order to better communicate the language settings across the webmaster’s internationalized web site. The tool offers debug details on missing return links from specific language codes, to unknown language codes in general.
Here are some screen shots of the beta tool that was shown by Google during their SEO hangout last night.
In fact, you can watch the brief explanation of the new tool at about 22 minutes into the video.
A big hat tip to +MenasheAvramov for spotting this.