Huddle is a Google+ feature unique to its Android and iPhone apps. It is not available on the desktop web interface. Huddle is Google+’s group messaging feature that can work with SMS (text messaging) but does not require it. Here’s a quick tip on how to control who can include you in a Huddle (group messaging).
1. Go to the Google+ web interface at plus.google.com
2. Select the gear (settings) icon in the upper right corner of the browser window
3. Select “Google+ settings”
4. Scroll down to the Huddle settings option near the bottom of the page
5. Use the pull-down menu to set who can start a huddle with you to one of the following options
5.b. Extended Circles
Select Extended Circles or Circles to limit who can Huddle with you.