This is ChatON, it’s an alternative to iMessage. It’s developed by Samsung, and is a free SMS and MMS alternative. Think iMessage or BlackBerry Messenger.
ChatON is already available for Android (it was released this fall) and now it’s on iOS. It’s also coming to BlackBerry and Windows Phone. This means you can text back and fourth with your friends at no cost. That is, if you want to ditch your current unlimited texting plan. Just make sure your friends all pick up the software as well.
The app is free, and it has some cool features, such as one that lets you draw pictures.