Google+ has been on a steady path of iteration and integration since its debut in 2011, and now it's getting a new universal login and sharing system called Google+ Sign-In. On one level, it's an answer to Facebook Connect: a single login for websites and mobile apps that lets users bring along some of their social profile information. The set-up is familiar: you log in with your Google credentials and are told what information the site or app wants to access (along with Google+ profile information, Google's other core services like Gmail or Google Calendar can also be utilized). You then choose what friends — or Circles — any related activities will be shared with, and you're on your way. A "private" setting prevents anyone but you from seeing your activities, and the system does work with Google's two-factor authentication.

The feature is available on the web as well as on both Android and iOS, though Android users get an added benefit: when logging into a site they can push any mobile app version directly to their phone. The real utility of this kind of service, however, comes with the social sharing functionality. Google's drawing a clear distinction between two types of sharing: things that are passively passed to Google+, such as the stations you listen to on TuneIn Radio, and items you proactively decide to share with others.

The former don't pop up in your friends' feeds at all — Google says it wants to avoid spamming — though the activity is visible if someone visits your Google+ page with the correct permissions. Over time Google does plan on resurfacing the information in scenarios when it's useful to users; when searching for music, for example, what your friends listen to could be a consideration. However, there are no specific features to that end being announced today.

Active sharing is a different issue. It acts as a direct post to the Google+ feed of the person you've reached out to, complete with a notification across all Google sites thanks to the omnipresent notification bar. Instead of just plain links, however, the items utilize what Google calls "interactive sharing." They appear as stylized cards with a specific included action — developers can add a "buy" button if you're sharing an item from a commerce site, or a "listen" button if you're sharing a song. Those buttons then kick you back to the related website or app so you can join in.

From the user perspective, it appears to be a refined riff on Facebook's system, with an eye on keeping as much noise out of your feed as possible. But while Google+ Sign-In has quite a way to go before it can catch up with Facebook Connect's ubiquity, the prospect of interactive sharing may prove to be a potent incentive for websites. One of the feature's launch partners is beauty review site Beautylish, and co-founder Nils Johnson tells us that for his company's business model, the new feature outpaces what the competition offers.

"It's probably the deepest integration we've seen from a commerce funnel perspective," he says, explaining that when users share a negative review of a product from Beautylish, the card simply presents the review. When a positive review is shared, however, it triggers an "add to cart" button that lets people start the purchase process right away. "In our category, reviews from peers are a big driver of people deciding to buy something, so having something like this is a really big enhancement."

Beautylish has offered both Twitter and Facebook Connect as sign-in options, with over half of the site's registered users taking advantage of the services. The draw is ease of use, says Johnson, but in what may be a sign of waning influence Beautylish is actually dropping the Twitter option today — and will be going forward with Google+ Sign-In and Facebook only.

With Fitbit, Shazam, Flixster, and The Guardian amongst the other launch partners, Google has a broad range of examples to show off the utility of its new system; whether it will help turn Google+ into the centralized hub that the company is continuously striving for still remains to be seen. Google+ Sign-In is rolling out globally now.