I have worked with a few projects using SMS enabled wireless devices for the communication of message commands to drive external devices that are wired to the sms receiver.

The system used email addresses from the wireless provider and we created apps using the SMTP protocol to send the data to the addresses. Then the wireless company forward the message to the device. This is the same method most cell phones and some pagers work.
It depends on the provider company.

We have a product called SMTP Wizard which would help in the transmission of the messages to the email addresses for delivery to the devices.

http://www.SeekfordSolutions.com/Products/SMTPWizard/

It has worked for our projects for quite a while and since we wrote it we know it works.

Good luck!