One of the great things about ColdFusion MX 7 is the Event Gateway architecture and the SMS Gateway in particular.
However, in order to get your SMS app live, you'll need an SMPP account for your SMS Gateway to use and talk to. Most of the major wireless carriers provide SMPP accounts directly (AT&T Wireless, etc) for access to a specific carrier's wireless customers, but for access to cross-carrier wireless subscribers, you'll need an SMPP account with what's known in the biz as a "Connection Aggregator". This company provides you a single, simple SMPP account, and then routes messages to/from the individual wireless carriers behind the scenes (using direct individual SMPP accounts for each, typically).
So who are these aggregators and where do you get one of these accounts? Here's a quick set of pointers to a few:
There are many others, of course, but these should help you get started. If you have feedback on these or others, drop me a quick line: firstname.lastname@example.org.