Since the release of Google Plus, a number of third party services and products have been released.
Many of these services require users to enter their Google+ user ID numbers to allow the application(s) to access user information such as the user’s profile picture or number of followers.
The best example I have of one of these applications, is the Google+ widget displayed on the right side of my blog.
See Also: Google+ “How To” Tutorial
Don’t forget to check out my other Google+ related articles!