Rob_Feature just tweeted about using SMS with Drupal, and yes, Rob, e-mail is the obvious answer. I don't know why I didn't think of that before!
OK, I don't know a lot about SMS, but am I correct that it's basically just email sent using a specific protocol on the provider's end? I know I can send what I believe is an SMS message to a phone if I know the email address for that account, which is usually something like the phone # @ the mobile provider's domain or some subdomain.
So I'm thinking about keeping church members in contact with each other, similar to the GroupTweet/Twitter model. Couldn't you just set up an email listserve, and have people sign up to it with their mobilie phone's email address? The Drupal module would create a block or node that would have a space for the 10-digit number, then a pop-up menu with as many providers as possible. On submit, the module would parse the number and provider into an email address using the given provider's required format/domain, then mail that subscribe request to the listserve. An unsub form would be handy, too. (Could be another popup: Sub/Unsub in the same form.)
Does this make sense? Would it work? Anyone with the expertise to put a module like this together? Am I misunderstanding SMS?