Google Plus' formal application for the iPhone are already available. This application is a free download from the AppStore.
This list of Google applications Plus feature on the iPhone with its description.
1) Circles Circles lets you divide things important to people right.
2) Stream Stream is the place where you got the latest things from your circle or see someone deliver things that are close.
3) Huddle Huddle is a super-fast group messages in your circle.