<phone number>@vtext.comas text messages to that phone number. Not all carriers support this, but most do.
mutt. Mutt offers a command-line GUI to help with message sending, but you can also construct command-line one-liners to include in scripts. In its simplest form, you can do the following:
ssmtpto send mail via SMTP mail hub, or if you want to just send raw mail, use
curlrequest to Textbelt is simple: