There were a couple providers that used to advertise on R & R's web site. I can't remember any of them. Show's how effective that advertising was.
Technically, it's really easy. All you need is an SMS client and any back-end software to drive your database applications. But the real issue that we saw when we looked at SMS was the $$. Getting your own SMS number is very expensive in the order of thousands a month. If you go with a provider, they want to keep all the caller fees for themselves. To us, unless we were getting a slice of that, it makes no sense to promote someone else's business for free.