Update (09/29/2014): Google Voice is now integrated into the Google Hangouts app and supports WiFi calling. For more information, please see this post.
Google Voice allows you to give out one number to reach all of the phone numbers you're using at a given time. The ability to schedule "quiet time," and organize contacts into caller groups really make Google Voice a handy service. However, making Wi-Fi or data calls is a feature that has yet to make it to the app. That's where Android apps like Talkatone, GrooVeIP, and Phone for Google Voice and GTalk come into play.
Using one of these apps will allow you to sign in with your Google Voice number/account and dial calls over a Wi-Fi connection. This can help you shave off some minutes from your wireless talk plan, and in some cases, provide a more stable call connection. While there are other choices in the realm of Android apps, these three are free and a good place to start if you're not sure Wi-Fi calling is for you.
First, you'll want to install a copy of Talkatone on your Android device.
Upon opening the app, you may be prompted to sign in. If not, tap the menu button on your device, then go into the Settings area. Press on the Add Google Account option, then sign in.
Note: If you have two-step verification enabled on your Google account, you'll need to log in to Google through a Web browser and generate an application specific password for Talkatone. This password will need to be entered only once (thankfully).
If you want Talkatone to use only Wi-Fi and not 3G/4G data, you'll need to visit the Connection area of the Settings menu. Here, you'll find a checkbox for Wi-Fi only. While there are lots of other settings you can tweak, the defaults for nearly everything are a good place to start.
To make a call, tap the Phone icon from the main area of the app and dial a number.
To remove ads or acquire better call quality, Talkatone offers in-app upgrade purchases. However, it's recommended that you test it out a bit to make sure it's fully compatible with your Wi-Fi signal, device, and personal taste before upgrading.
This version of Talkatone is a step above the other choices, because it allows 3G/4G calling without requiring an upgrade; but it does sacrifice some of call quality to remain free of cost.
Install GrooVeIP Lite on your Android device to get started. This is the free version of GrooVeIP; it is ad-supported and allows only Wi-Fi calling. The paid version is available through Google Play for $4.99 and also supports making calls on 3G/4G connections.
Open the app and tap the Google account you want to use for sign-in, then authorize access for GrooVeIP. If you don't see the account you want to use listed, just press the manual sign-in button and enter your information.
There are some settings you can adjust without upgrading, but starting with the defaults is a solid plan.
To make a call, tap on the Phone icon along the top of the app and dial a number.
GrooVeIP Lite offers excellent audio-adjustment settings to make up for its lack of free 3G/4G without upgrading.
Phone for Google Voice and GTalk
Start by installing a copy of Phone for Google Voice and GTalk on your Android device. This version is ad-supported, and unfortunately, at the present time there is no paid version to remove ads.
When you open the app, you'll be prompted to log-in with your Google account details.
To make a call: tap on the round button labeled Keypad and dial a number. You can also choose from Contacts if you don't know the number by heart.
A major drawbacks to using this app over the others is that it doesn't support 3G/4G calling. However, Phone for Google Voice is a great option if you don't want too many customization settings and want to get started with Google Voice Wi-Fi calling immediately.
What do you use for Wi-Fi calls with your Google Voice number? Share your favorite apps and experiences in the comments below!