Configure IO element "External Voltage" with "Generate Event" option as "On Exit".
Set low level to like 5000 and hi level 30000 for example. And thus in the event voltage drops below 5000 or above 30000 -> you will get a record. Which will be sent to server.
Now regarding sms events:
GSM -> SMS events -> enable external voltage sms event. Configure gsm number for it. And sms text. And once a record is created according to external voltage IO -> you will also get sms.