If you want to check Google+ notifications on your iPhone quickly, here’s a handy technique. Google’s search site tunes itself for the platform it sees. On an iPhone tapping the “more” link in the upper right hand corener (see above).
If you tap the “Notifications” tab, you’ll will be taken to a list of notifications from Goolge+ (and, perhaps, other Google services). You can see a list of my notifications in the screenshot below.
If you bookmark this page and, optionally, pin it to the iPhone’s apps page, you can quickly check for Google+ notifications without running the Google+ app itself. This technique can also work on an Android phone. However, Google+ provides sufficient rich push notifications to its status bar which reduces the need to check a list of notifications.