I have a pretty straightword apps to rollout on iPhone, Blackberry and Android.
The process flow is as follows:-
1. User makes a call
2. The app intercepts the call and queries the handset GPS functionality to get current country
3. The app queries the handset WiFi functionality to work out if theres access internet access
4. Based on the country & WiFi presence, the app presents the user with 3 choices of how to make the call (I will provide these)
5. Based on the selected choice, the app places the call.
Thats it. Only experienced freelancers should bid for this as I will only work with those who have done similar.