Yet apparently not business accounts. You can use the integrated hangouts in gmail, and the phone apps, but hangouts.google.com says it's not an enabled app for your account, and I can't seem to find where it's available to enable/add in the admin console (that is, I can find where to enable and add apps, but it isn't listed, and I'm a super admin). The Apps marketplace has third party apps, but that's not what I'm looking for.