Alex Wiesen of Google announced the new feature his his own Google+ account, saying that this should make things easier for people who are working on their laptop but don't have a smartphone nearby to make a call. He stated:
To make things easier, we've just added Hangouts as an option when making calls from the web. It works even if you aren't using Hangouts in Gmail, and doesn't require a Google+ account. Try it the next time you place a call from the Google Voice website -- I think it's a much easier way to keep in touch with people.
At the moment, this feature is only available via the Google Voice site. What do you think of Google adding in this small but very useful feature for Hangouts?