This is a custom/non-standard attribute, so I can't imagine it being catered to in a stock app in this way (though only the developer could really speak specifically to this request--just seems unlikely to me).
In the meantime, there are several community options that can do what you want, as well as other built-in options. I'm not sure if any others are still being maintained, but one of them is mine if you are not familiar: [RELEASE] Device Activity Check - Get notifications for "inactive" devices.
If you prefer something built-in, a Rule with a "custom attribute" trigger can do what you're looking for with this Notifier instance. (And, in fact, my custom app isn't exactly the same--it doesn't subscribe to any attributes but rather just checks the attribute or device metadata, depending on your configuration, in response to the schedule or whatever "triggers" you have set up.)