This is no different than sending regular email. You just need to lookup what syntax your cell provider is using for this. It is usually something like xxx-xxx-xxxx@sms.cellphonecompanyname.com. From there you can use the regular JavaMail API or the Jakara Commons Mail API to send the email to it.
Keep in mind that you can usually only send 100 - 200 character messages generally, and most cell companies charge for SMS so you may want to include some throttling logic in case something goes wrong. You dont want it to start sending hundrads or even thousands of messages if something goes wrong.