First of all, all text messages are in-the-clear (at least for the service provider). Second, this seems to be a service that is targeted to end-users and itsel

First of all, all text messages are in-the-clear (at least for the service provider). Second, this seems to be a service that is targeted to end-users and itself uses the API of one of the big "cloud telecom" providers. If you want API access, I would suggest bandwidth.com, Plivo, or, Twilio.