Others may find this tip useful, as I have:
Send an SMS Text Message from the Command Line (Thanks to
Topher Kessler for posting the link in an earlier incarnation.)
(I don't know about other ISPs, but with Verizon, a text sent via Terminal and responded to - as a text - to the sender's e-mail address yields an e-mail address that can be used for future texting without having to work through Terminal.)