I definitely understand that it would be ideal to have a built-in integration configured to accept SMS messages as a form of an event that could trigger an incident within PagerDuty.
Right now, the suggestions similar to what Chris Ford indicated are the best way to go!
There are many systems out there that convert SMS messages into an email/webhook/phone call but it is another system to monitor and maintain.
I’ll share this feedback with our Product Team though as it would be great if we could support more systems without access to data.
As you had mentioned the device is a sim-enabled transmitter, is there a possibility that it could leave a phone call instead of an SMS? Then the Live Call Routing feature could be useful! You could force it to leave a message and that data would then notify the user on-call with an incident.