The site was written in .NET and really did not require a whole bunch - the real trick is coming up with a way to automatically determine the reciever's cellular service provider. for the time being I have a bunch of options to choose from. However, the hardest thing to track down was the actual domains for each provider.
Here is a list of what I have in place so far.
Then a simple CDO.Message and you're done...
http://www.text-send.com