I´m still looking for an appropriate cheap modem that will work with an Arduino board.
In the meantime, is there any way I could simulate a GSM modem? I mean, can I use the terminal from my Ubuntu computer to pretend that it´s a modem by sending the right AT responses to the arduino via FTDI ?
I feel bad advertising for myself, but I designed this cellular module specifically for people wanting to prototype.
http://themakerspace.com/index.php?main_page=product_info&cPath=5&products_id=6&zenid=47f47748d76d342b0c6386c506b70dd4
Not sure about simulating, but theres not much to simulate. Just listen with a USB to TTL device on the UART Tx of your microcontroller to see if its sending the right AT sentences.
Good luck!
Thanks.
I don´t have the budget for such right now. So i´m looking to emulating a modem for now. 
I feel bad advertising for myself, but I designed this cellular module specifically for people wanting to prototype.
http://themakerspace.com/index.php?main_page=product_info&cPath=5&products_id=6&...
Don't feel bad - looks like a great solution that I'm sure many would welcome to hear about. Do you have an example of hooking this up to an Arduino?
Cheers,