Until now, iPhone users have been restricted to using the Google+ mobile website in order to use the social network.
It appears that the Instant Upload feature has not been ported from the Android app yet. Instant Upload automatically adds any photos and videos captured in the Android app to your Google+ album. Perhaps this feature will be added in the future.
The Google+ app for Android devices was launched on the first day that Google+ started its limited field trial, but it has taken until now for the iPhone app to make it through Apple’s review process.
To check out the Google+ app for yourself, you can download it on your iPhone now.