My wife is currently in the UK and is using a ZTE Blade running Android Froyo 2.2 I am in the US with an iPhone 4. We both have unlimited data packages. What is the best app for us both to run to enable us to make free calls to one another AND ALSO for the phone to ring / notify us even if the app is not running or only running in the background. In other words for it to work just like a normal phone. I know skype doesn't push new call notifications on the iPhone unless the app is actually running.