Can you expand some more - does this software connect to a modem to send SMS's to nearby phones? Is this software similar to a stingray device, or am I misunderstanding this?
By modem we mean any GSM Modem device. Like a USB Data Card used for internet access, or a mobile phone connected via USB. You can send SMS anywhere. Software just allows you to use your phone / usb data card to send messages.
It just connects to the cell phone network like any other mobile device you have and then sends the SMS using the standard infrastructure.