A friend of mine was implementing SMS text messaging in his application, in which a one way text message was sent to a user alerting them of some action. I was intrigued, so I looked into what options were out there. NOTE: I have no experience in using these servies or implementing them in my applications, so I cannot vouch for these solutions. I imagine each has their benefits and limitations, which unfortunately are usually found during UAT or later.
However, we can achieve texting to a user’s machine very simply through an existing mechanism: email. Sending an email address to the provider can redirect the message to a user’s phone as a text message too. There is a complete list of email addresses for providers at http://www.emailtextmessages.com/. I also found another useful list at Wikipedia, which contains a brief overview of the format the message should be in. Certain providers require different formats of the body message.