This has the benefit over groove ip / sipdroid in that it still allows you to receive calls in Gmail. In addition, I found the call quality /delay in groove ip to be AWFUL.. This call quality is on par or better than tmobile wifi calling.
This guide presupposes that you use Google voice. This will work on ANY ROM as long as it has been deodexed.
I know it sounds complicated, but it's really pretty simple if you follow the steps... And pretty foolproof. It took me about 15minutes from beginning to end to do all of this.
Step one: configure incoming:
1) set up a free SIP account with Callcentric.com . Once it is set up, click to 'add features' and add a free incoming number(note: if you don't want to pay for 911 services, you have to say that you're not in the US).
3) setup a sip app on your tablet (i like csipsimple.... Free in the play store) and connect it to your callcentric, account (user name is your callcentric sip number... Should start with 1777)
4) go to Google voice on your computer, go to settings, and add a new number. Add the number you were given by Callcentric (the phone number, not the 1777 number) . It will call and confirm you. It should ring through to your tablet! You now will receive incoming calls to your tablet! (note: if it can't 'hear' the numbers you are dialing, hang up, increase the volume on your tablet, and try again)
Now, let's get you set up for outgoing calls.
1) download voice+ from the play store and connect it to your Google voice account.
2) download exdialer from the play store (dialer one doesn't work... I don't know why)
Now you have two options. You can:
A) go here and use this nifty utility to modify your ROM for you http://forum.xda-developers.com/show....php?t=1877891 (thanks Mateorod!)
or B) modify your framework-res.apk to make the tablet think that it is voice capable so that voice+ will be triggered when you make a call (this is what the above utility does for you).
1) download the framework-res editor that is attached here and unzip it
2) copy your framework-res.apk from your ROM (found in the /system/framework folder) and put it in the 'place-framework-res-here' folder
3) double click on 'run me' and decompile your framework-res
4) in the 'files-to-edit' folder, click on framework-res.apk>res>values>bools (edit the bools.xml file)
5) find the line for 'voice capable' and change 'false' to 'true'. save and close the file
6) in the framework Flasher that you opened in step 3, choose '2' and compile a new apk
7) choose option '3' and sign the apk.
8) choose option 4 and create an update.zip
9)flash the update.zip that you made
10) click 'thank' for my help in making this guide
Note: if you are getting an error about "echo off", you probably don't have java jre installed. Install that, and you should be good to go.
Done! You now have a fully working soft phone!