Callback for Android can really make your calls cheaper. NoNoh.net callback web-service turns your outgoing calls to incoming.
How does it work? You enter two phone numbers: one is yours and the other one is number of a person you want to call. NoNoh.net server calls your number and then calls the other one, linking those calls together. So you don't need to pay for the outgoing call. Callback is much cheaper than traditional phone call, especially for international routes.
Main features of Callback for Android:
-automatic balance update
-address book integration
-simple interface and settings
-ability to make phone calls between any two phone numbers even if they are not yours, e.g., you can arrange a call between your home phone and your friend's mobile
Important: Valid NoNoh account is required for this app to work! Sign up for free at http://www.nonoh.net/en/websignup.php
New features are coming with future updates:
-support for new callback providers