I'm looking for a web service which allows me to send an SMS to it and then it calls a HTTP callback. So, for example, I can register on the site and it provides me a user id and if I send an SMS to the service's phone number with my user id and some extra parameter (e.g. a command) then it calls the HTTP callback (which I gave to it previously) with the command I sent in the SMS. It could be used to control web applications via SMS if the user has no mobile internet access.
So it's a programmable web service which provides an SMS API instead of a HTTP API. An SMS to HTTP gateway. Do you know about a web service like this?