Hangouts Dialer

Hangouts Dialer is an official app from Google that lets you make phone calls from the Hangouts app itself, very similar to the functioning of apps like Skype or Viber.

After installing Hangouts Dialer, you'll notice that the Hangouts interface has changed slightly to accommodate a new tab from which you can dial phone numbers (or select names from your contacts).

To make these phone calls, you'll need to have credit (as you would with other apps of this type). The only exception is if you want to call another user that is also on Hangouts Dialer, in which case the call is made over WiFi or 3G.

Hangouts Dialer doesn't offer any more features than the other heavyweights in the field of VoIP calls, but it has a fundamental advantage: it's integrated into Hangouts. Although it is installed independently, Hangouts Dialer meshes perfectly with the Hangouts interface.