Perhaps Sense has this… I am not sure. If sense is not able to detect a signal or is off line, can it push a notification? I am thinking if I am away and want to be notified of a possible power outage
The Sense mothership alerts you when Sense has been offline for a while… I forget the maximum amount of time it can be offline before you get the message. But that could be power outage, internet outage, etc.