Exchange data between Iphone (App) and gsm modem

Im' trying to implement an App which is able to conect to a remote GSM Modem. To etablish something like this I need a dialin process in the app which call the "Phone number" of the remote Modem and exchange data with it. On the GSM Modem is no posibility to connect the web. It can only accept incoming calls 开发者_如何学JAVAand response.

Does anyone know if there is a practiacal solution?

No not really, there is no way to use the any of the phone functions (meaning voice/data) other the internet connection. You can't dail a number and then send data of the line, because as soon as you dail the phone app closes you app (or backgrounds it) and takes over.