I'm not sure how it's work, I'm just thinking out loud.
Under SMS Media Server> Inbound Routing, there is a workflow. You can add a "SMS" tool in it and set some variables for that. If you could be able to match those variables with, for example the world "Help", then you can definitely be able to pass that to a "Web Service" under "Execute" tool and send them what ever you want.
Just check that and let me know.
Thanks