Sending Alerts via SMS Text?

How can we have PowerAdmin send us SMS text alerts when the Internet connection goes down?
Some background:
1) The Internet connection is down, so we can't send the text through a carrier's SMPP gateway and we can't send it as an e-mail to push it to text through the carrier's system.
2) We cannot connect a redundant Internet connection for security reasons.
3) We cannot use wi-fi for security reasons.
4) The PowerAdmin server is on a virtual machine that might be moved between hosts, so an internal modem or external com/usb connected modem or phone won't work.
5) We need something that has an external antenna that can be located where the reception is.
6) The solution cannot accept inbound texts or connections - outbound only.

It would seem like there is hardware solution somewhere that connects an SMS gateway to your network via Ethernet that can use an outside antenna and have a firewall or configuration that prevents incoming connections. We've searched for SMS Gateways on Google, but most seem application specific or require you to write custom code using an API. We are willing to spend some money and even add a separate firewall between the network and the gateway if needed. Anyone done this?