While Facebook has been rolling out features this week with improved lists and subscribe buttons, Google+ has stayed quiet for the most part. Now, however, Google+ is releasing part of their API for developers saying, "This is just the beginning". This means there will now be outside applications for Google+, however, they have laid some pretty strict rules for third party developers. Some of the principles Google has laid for their developers include, "put the user first, be transparent, and respect user data". The API was released on public data only, which means they can only retrieve public posts and public profile data.
Developers note that there are not a lot of APIs in this release, and it only allows for querying of a single person or an activity/action on Google+. So third party apps like Tweetdeck or HootSuite could be created to display what's going on on Google+, but they will not let users post to Google+. Because the APIs are so simple, the app approval procedure is also simple, they only request to know who the developer is on Google. Given that this is only an initial release, more releases of Google+ APIs are sure to come. Which means more potential for Google+ to be more ubiquitous.
Source : Google+ releases API for developers