Nymgo

Nymgo provides all the features you want from a call in one place. Easy-to-use multitasking app with enhanced calling features App synchronizes address book contacts across devices Smart user interface. Crystal clear, anytime, anywhere. The highest quality calls from your iPhone to any mobile or landline in the world. Serves all your communication needs. International & local calls at the best rates SMS text messaging. Always know how much you are spending. Rate finder See how much the call will cost before you make it Credit tracker.

What is new in this release:

Synchronise feature to instantly share address book contacts across all your devices.
Automatic switching between WiFi and 3G networks so you'll never lose a call.