iPhone Users: Not to Worry, Google Hasn’t Forgotten You
Google has developed a Google+ app for iPhone, but apparently the delay is on Apple’s end as the app is being reviewed.
In the meantime, Google+ has a mobile site set up if you go to plus.google.com on your iPhone, you will get the mobile version of Google+. (Of course, if you don’t have an invite yet, you’ll have to wait for someone to send you one or sign up for Google+ to notify you of updates.)
See this article: While We Await The Native App, The Google+ iPhone Mobile Web App is Pretty Solid.