I have played with all kind of variations of VoIP schemes on Android. This is possibly the best, most useful, tightly integrated, easy to set up solution for making FREE incoming and outgoing calls, from or to any US number, without the other party having to know where you are or anything other than that your US phone number rang, you answered it.

GroVeIP. $3.99 on Android Market. The Voip calls are free. The app costs $3.99 (TOTALLY worth $3.99)

It is a transparent frontend client for free Google Chat VoIP, and Google Chat is seamlessly integrated with Google Voice, all of which are free Google services so other then the one time $3.99 to buy the app, unlimited free calls to/from US numbers are 100% free anyplace in the world you have any form of 3G or WiFi.

It will also work concurrently with any cellular companies SIM, US or abroad, so say for instance I am in Angeles City with a Smart Buddy SIM and a prepaid unlimited Smart 3G plan turned on for 50 Piso/day or 300 Piso/ week. I call my sweetheart in AC at a local Philippine number, it routes through Smart's ordinary cellular network as an ordinary prepaid cellular call. Then later I’m in a bar and my office in the US calls my US Google Voice number. GrooVeIP seamlessly and transparently routes the call from the US, over the internet, through Smart's 3G Data network to my Android phone and it rings, I answer, my office knows none the better that it is anything but an ordinary call, it doesn't cost me or anyone else anything other than paying for the 3G Data service. Later I call back to a US number. Same thing. Free, transparent, person I called gets my ordinary US Google Voice number for Caller ID and never knows it is anything unusual. Then later my sweetie in AC texts me asking me to "PasaLoad", it comes in over Smart’s ordinary cellular network as an ordinary SMS message. The integration is fairly seamless.

Voice quality is very good so long as you have 3G or WiFi good enough to maintain a 80kbps continuous two way data stream. That should be very easy for any decent 3G or Wifi but if you have crappy third world internet connectivity, that is it's one big weakness. If the internet connection is inadequate to maintain a continuous 80kbps data stream the call will break up and have drop outs. There might be a slight lag too based on network latency. That is an unavoidable problem with any VoIP.

The continuous "keep alive" data pings also tend to use up your battery a bit faster and don’t use it on a "non-unlimited" prepaid 3G SIM or you may use up all your load/pulsa/whatever rather quickly from the keep alive pings necessary to keep it available to receive incoming calls.

Prerequisites? Almost any Android phone (Android 2.1 or better), have or else open a free Google Voice account. Pay $3.99 and download the app from Android market. In your Google Voice account set it to forward calls to Google Chat or your G-Mail account (you should already have a Google Chat account as a side effect of creating a G-Mail account when you signed up your Android phone if for no other reason). WiFi or 3G data connectivity from any source. Fire up the app and log on to your Google account. That’s about it for the setup. You can set it to autorun and autologin every time you turn on your phone so it's always on. There are a few settings you can tweak to fine tune it a little but nothing complicated like previous free VoIP schemes I have put forward and this one works more reliably too.

Just thought I'd add I've now given this app a fairly reasonable workout in the field. I tried it in Hong Kong on the Wifi at the airport lounge, and in the Philippines on both hotel Wifi and prepaid 3G from my Smart Buddy SIM card. In all cases I have excellent call quality to and from the US. It's an almost perfect transparent system where my US number is always available to anyone who wants to call me, and I can call anyone I need to in the US without revealing my out of the country status. And the best part is other than $3.99 for the app and the 50 Piso/day for prepaid 3G for when I don't have Wifi, the rest of it is FREE.

Any recommendations for IPhone apart from the Skype App? GroVeIP is not available in the apple app store. Thanks!

Actually they claim to be working on a version of GrooVe IP for I-Phone. No release date mentioned yet but it is implied it will be soon.

Otherwise, I'll have to defer to others on I-Phone apps since I personally know next to nothing about I-Phone's in general.

For the I-Phone crowd, this app looks to be the comparable I-Phone equivalent. Talkatone http://www.talkatone.com/ apparently free in App Store. I cannot comment on how well it works on an I-Phone or how tightly it integrates because I don't have an I-Phone to play with but at a glance it DEFINITELY looks like an app I would try out if I were an I-Phone kind of guy.

As for the GrooVe IP app. I also tried it in Japan on airport lounge WiFi. Worked great from there too. I want to use it a little more before totally say it is the greatest thing ever but up until now this app is looking like a game changer for overseas to USA phone availability. (for those of us who need to be available by phone even when we are away)

Sancho, THANK YOU for finding this. Just downloaded will have to see how this compares to Skype in the field next month.

I Agree Globe 3G Is sparatic at best!