For many of its 750 million users, Facebook serves as handy virtual address book and Rolodex, an organizing framework for relationships. This week it took another step toward its other ambition: replacing email and SMS.

On Tuesday it introduced its first standalone app outside of Facebook called "Facebook Messenger," available "soon" on Apple iOS as well as Google Android devices. The app continues the theme of having all Facebook user messages threaded together, whether they are messages, SMS or chats. The app was created by the team behind Beluga, a messaging service startup that Facebook purchased in March.

"The Messenger app is an extension of Facebook messages, so all your conversations are in one place, including your texts, chats, emails and messages," Lucy Zhang, Beluga co-founder and Facebook engineer, said in a blog post. "Whether you're on your phone or on the web, you can see the full history of all your messages." Additionally, users can see friends' location on a map and attach pictures. The location feature can be turned off in privacy settings.

Other than the actual Facebook app, Facebook Messenger is the company's first feature app released on its own and could be an indication of others soon to come. For example, could there be a standalone Facebook Photos app (as TechCrunch predicted in June) or a Facebook Events app. With the Google+ social network out for more than a month and creating a significant industry buzz -- as well as steadily gaining membership -- Facebook is ramping up efforts to make sure membership doesn't start slipping over to its biggest competitor. The Google+ phone app already has something called Huddle, a group messaging and chat feature.

David Berkowitz, 360i's senior director of emerging media and innovation, believes this release is part of Facebook's strategy of keeping the users it has happy. "Facebook is getting to the point that in certain countries -- like the U.S. -- there's not going to be much more growth," Mr. Berkowitz said. "Most people who were going to be on Facebook are already on it, so making things easier for users who are already on it is a smart way to go."