Also, a little known fact is that you can send SMS to an email address (as an email). For example, if my number was 555-555-5567 on the AT&T network, the corresponding SMS email address would be
5555555567@txt.att.net. I've included a link below that shows a number of these services, which differ by carrier (1). The general rule with SMS applies to the email sent to the carrier's relay. The message may be chopped up into 160 character chunks, and stopping after some unknown number of chunk, so you'll need to keep the message short.
(1)
http://www.howtogeek.com/howto/27051/use-email-to-send-text-messages-sms-to-mobile-phones-for-free/