This is a subject near and dear to my heart.
I have a custom alarm. System on my boat.
It monitors
Bilge water, 2 sensors
Shore power
Inverter power
Battery voltage
Cabin temp
Engine room temp
If anything goes beyond my alarm point then it texts, and e-mails me.
Alarm messages repeat at a frequency depending on the severity.
Communication is via the cellular network or satellite network if cell is not working or out of range.
I can also go to the unit and view its status via a web page.