Reply To: Email to SMS – Texting into the Show
If you already have a non-Google Voice number (one is needed to establish GV service, as an initial forward-to phone number), the easiest way to SMS without cellular service might be to establish a GV number.
The trickier part might be how to automate sending SMS with it, if that was your aim. (It’s relatively easy to automate sending emails.) You’d have to reverse engineer what the Web pages do, but it would seem feasible to use that. There are a few folks who have done similar things, and have cobbled together PHP, Python, etc. packages to interact with GV. See http://stackoverflow.com/questions/1668619/is-there-a-google-voice-api