Hi Robert,
I go through your link and read the full article as well as read its prerequisites section in which all hardware and software requirements are given. I hope you have all compatible software and hardware, I would like to suggest that first of all you need to find a way, where you are allowed to send free SMS. There is no direct connection between the internet and the phones, so you need to find someone who acts as gateway. And then you can use the given gateway. If you are lucky, the provider will give you a nice API (e.g. a Webservice) you could use. But normaly a SMS cost money so it can be hard to find such a provider.
Regards
Amit
.Net Training Indore