I've recently resurrected our two-way SMS service for use by my students in their current coursework, a site to gather and report results for their chosen team sport. I require an exotic interface to the data, for example a speech interface with Opera or an SMS interface. In my SMS installation, the first word in an in-coming message is used to determine the service to which the message is to be routed via HTTP, and the reply if any is then sent via our out-bound service to the originating phone. The framework was originally implemented in PHP, but individual services can be in any language. There are a number of mainly demonstration services implemented. XQuery is used to implement a decoder for UK vehicle license numbers. This is also a nice example of the use of regular expressions. By comparison with the original PHP script, the XQuery version is both cleaner and more general. However there is no regexp function in XQuery which returns the matched groups in an expression, so this is perhaps bodged with a wrapper around the XSLT2 analyze-string function.
http://en.wikibooks.org/wiki/XQuery/String_Analysis#SMS_service