because SMS uses phone numbers it's a big difference to email.
At first Joomla itself doesn't provide classes for this so it must be implemented directly in JEM. Theoretically it could be possible but for each recipient an sms number must be available, the admin has to specify a service provider which bridges between internet and phone networks, the api must be well defined, and last but not least the web provider must allow to activate the corresponding php extension required.
So I think that's too much for us. When Joomla provides SMS support we can talk again about this but at the moment I see no chance for this, sorry.
