Update: Hangouts 2.3 is now rolling out to devices in stages. If you rather not wait, we can help you download it manually. And as it turns out, this Dialer just links to a tab within the new Hangouts app. It is not a separate, standalone piece of software.
Hangout's Google Voice integration is finally happening. We started seeing functionality merge into Hangouts overnight, but there remain a few kinks to work out that we're hoping an upcoming app update will fix. Until then, Google has hit the Play Store with a dedicated Hangouts Dialer app.
This app expands upon Hangouts with the ability to make phone calls. Users will be able to place calls to any phone number in the world, with most calls to the US and Canada being free. Communications between two Hangouts users will also not cost a thing. In addition, people can connect a Google Voice number to use it for VoIP calls instead.
After the app's installed, users will be able to access phone calling features from within the regular Hangouts app and the web as well. Dialer requires Hangouts version 2.3, which we're still waiting for Google to roll out. Patience, folks. The wait is almost over.
The APK is signed by Google and upgrades your existing app. The cryptographic signature guarantees that the file is safe to install and was not tampered with in any way. Rather than wait for Google to push this download to your devices, which can take days, download and install it just like any other APK.
File name: com.google.android.apps.hangoutsdialer-0.1.74972069.apk.
Version: 0.1.74972069 (Android 4.0+).
Source: Google blog