From Development Seed's Tm McWright: "Using an GSM modem or cellphone, SlingshotSMS will send and receive text messages on behalf of your web application. It builds on the work of pygsm, an excellent Python library for dealing with AT-compatible modems. What this means is that SlingshotSMS is compatible with Mac, Windows, and Linux, and can interface with a wide range of GSM modems and cell phones – including many sub-$200 field-ready modems like the one we used for testing when we were field-testing last week as part of our participation in Camp Roberts experiments. All code is available on github