We are constantly listening to feedback so that we can make Hangouts even better for Google+ users, and we're excited by the really cool ways people are using the product. Today we’re making it possible to make phone calls from inside a hangout, so you can dial people into the room from wherever they’re at. (Helpful for party lines and conference calls alike.)
This new feature is initially available inside Hangouts with extras (plus.google.com/hangouts/extras), and we currently support calls to the US and Canada (for free, in fact). The steps for adding a telephone participant are straightforward:
1. Click Invite at the top of the hangouts with extras window
2. Click the Phone tab on the left of the window, and enter the phone number you wish to call.
3. Click Call now.