Hello, I'm Anuj, founder of Zip Phone and I'll be here all day to answer any questions that you might have. Zip Phone started as a small personal project, but has quickly grown into much more than that. I hope you enjoy using it as much as I do :-)
Pretty neat project. I love seeing the base integration with the Android OS. And I think it's a wise move to have some sort of app on iOS. I'm an iOS user myself, however I can't run your app since I'm still on iOS6. I hope Apple allows this type of integration in the future (but I'm sure the carriers will take some type to get used to the idea of making money off Data instead of voice.) Good luck!
In my opinion Apple will never let a third party develop something like Zip Phone (for android) that has the ability to automatically route phone calls away from the cellular network. Not just because of their carrier relationships, but also because it goes against their philosophy of tightly controlling all aspects of the user experience.
I thought that about their keyboard too but they just opened it up in iOS8. I believe things are changing.