Well here is a good news.. You can use VoIP calls from your android device. You need to do two things
1) Enable hangouts instead on talk in gmail.
2) Download opera browser (any browser that can fake a desktop UA might work. I use opera)
Now, change the user agent to desktop in opera browser and call using hangouts in gmail like you usually do on a PC and it works!!!
If you already knew this, good for you. I didn't and I just found out so I am sharing an option till Google releases full hangouts Google voice integration.
EDIT: if you are logged in and opera is running in the background, you can even receive calls to your Google voice number!!!
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