Check this plugin: https://github.com/Dynatrace/Dynatrace-AppMon-SMS-Notification-Plugin
If it does not work as you need you will need to create your own based on this one. Sources are available on github as you see 🙂
Use this plugin, set it as action for incident and that’s all I think. You have to be more specific 🙂
In general I think you should take this plugin and make the one you actually need based on this. This is using mostly specific api for sma sending or using usb device. You need just execute url with phone and message as parameter. It’s pretty simple action in java.