Callback generator

We need a small Android application. The application will contain 2 fields: - My phone number - to enter a phone number - International prefix - to enter a calling prefix 011, 00 etc. The client enters his phone number in the field "My phone number" When making a call if the prefix field is blank, the application should offer to choose the dial mode: - VoIP Call - Regular Call If the prefix isn't blank all the numbers that match with the selected prefix, should be called via VoIP, the rest via Regular calls, without asking to choose. When VoIP call is chosen the application sends an HTTP request via HTTP post. The request will include both client's and dialed numbers, as well as the prefix.