I was looking for a way to convert a google+ feed to an rss feed (because rss is pretty universal, and it’s easy to read however you want, thunderbird/google reader/phone app) and found that there is no way to do this directly in google+. I found a reference to an older app which apparently no longer works. After a little more digging I found a working solution, http://gplusrss.com/, allows you to create a feed of your activity. I tried it for one of my friend’s profiles, but was not successful. Not sure if that’s due to their privacy settings or because of the app.
For your own feed just run to the website and hit the login via google+, for a friends feed you need to get a google+ api key code and then the userid of the person (from the web address, it’s the long number), and it will create a feed for you.