GOIP appears to be a network to GSM gateway, however GSM is dead in an awful lot of places these days. And SMS marketing should die ;). But, it seems like this functionality (if you don't want to use something like Twilio) could be implemented as a phone app, rather than requiring a special piece of hardware.
Two of our customers who were interested in SMS marketing or SMS WiFi login are on some tourist heaven islands and Twilio is expensive there so they used GoIP on their own as it's way cheaper to send local SMS there without the need to go outside to the continent.