I'm interested to know what you plan on doing for revenue. I'm sure the cost of the calls will quickly outweigh the $.70 you're getting out of the app store.
Other than that its a great idea which I'm certain people would be willing to pay for (I would be if it was available internationally)
We're still figuring all that out -- for now, we just wanted to focus on making something that people want (ie, use).
Beyond that, we've got a couple of ideas that we'll be testing out -- maybe selling a brandable widget-based version to businesses, affiliate links, etc.
Not sure what will end up working but I can assure you that we'll be iterating pretty quickly. :)
Other than that its a great idea which I'm certain people would be willing to pay for (I would be if it was available internationally)