After some experimentation I have successfully got a Stream Entry in GooglePlus to be published to Twitter, Facebook and Blogger. The secret to achieving this is Posterous, although I expect that Tumblr could do the same. You can use almost any service that can accept an email as input. 
Here is the process to setup email distribution.
Setup Posterous
The first step is to setup your account on Posterous. my site on posterous is http://ekivemark.posterous.com. Configure all of the services you want to automatically post to. For me that is:
- My Main Blog on Blogger - http://ekive.blogspot.com
- Identica
- FriendFeed
- Flickr
- YouTube
- Delicious
Run a test post to make sure this is working. If everything is okay the next step is to integrate GooglePlus. The secret is that services like Posterous need you to identify the email addresses that are allowed to publish posts. i.e. A contributor/administrator rather than a subscriber. We need to setup the GooglePlus email as a Contributor.
Get your GooglePlus Email Address
When you publish a stream entry to someone without a GooglePlus Account they receive an email with an address like this:
"Mark Scrimshire (Google+)"<noreply-xxxxxxxx@plus.google.com>
To get the address create or forward a stream item to a non-gmail email account I.e.. NOT the account you use to sign in to GooglePlus.
Get the email address from the relevant inbox.
Add GooglePlus as a Contributor in Posterous
Go back to Posterous and the Blog Management Page.. Go to the People Tab and click on the "+ Add People" button and enter your GooglePlus email address. Add them as a Contributor. Unfortunately Posterous only gives you options to receive an instant email or a daily digest of posts. Select the daily email option.
If you are using another service this step will only work if that service does NOT require a validation step. The GooglePlus email address is a no reply mailbox so you will never receive a validation email.
Setting up GooglePlus
Now that you have Posterous configured to receive posts from GooglePlus you will want to add Posterous as an email contact in to one or more of your circles. I created a "Broadcast in SocMed" circle that I can add email addresses to.
Posting to Posterous
There is one step to remember when you want to post to Posterous from GooglePlus. When you select the Circle to share with you have to click on the circle name and click the "Notify about this post" check box.
Now share the stream entry.
Tailoring GooglePlus for Social Media Posting
If you have configured Posterous to AutoPost to Twitter then you will want to think carefully about the first line of your Stream contribution. GooglePlus takes part of the first line and repeats it in the subject line of the email. So a stream entry that begins like this:
"This is another test to integrate GooglePlus with other Social Media Channels. Including a link to my last GooglePlus Post"
becomes a subject line of:
"This is another test to integrate GooglePlus..."
This gives you about 44 characters that will get propagated as the title of your Posterous Blog post and as your post in to Twitter etc.
Think carefully about the start of your stream entry. If you include hashtags, such as #GooglePlus then these should appear in your tweets posted via Posterous.
In Conclusion
This is not ideal. It is a one way channel. I am really waiting for TweetDeck and Posterous to be able to use a GooglePlus API to allow me to post from their platforms in to GooglePlus. I also can't wait for TweetDeck to add GooglePlus as a stream in to TweetDeck. However, I am not going to hold my breath on that one. I suspect that would require Twitter to get their hands on the firehose from GooglePlus. Given that the two companies have let their Twitter to Google Firehose deal lapse I have my doubts that TweetDeck's new owners will want the GooglePlus streams as a feed.
