Where SMS is going to be deployed in an enterprise environment, it may not be feasible to have a web port accessible to be given the message via HTTP POST - in this instance it would be beneficial to have other options available such as:
Additional HTTP commands for:
List messages in queue
Retrieve message X
Additionally, there are other protocols which would be ideally suited to this scenario as another option such as POP3 or IMAP, making the inboxes available via POP3 would also then make a seamless integration to email systems without them needing to be forwarded in to an existing email system.
Regards
Matt.