Hello, from what I can see from your question, I assume that you are requiring a regular update to the device (a Thing entity)
My question is, how is the Thing updated? Some random properties get a new value in a random time or all the properties get changed?
BTW, the String property only have "equal" "not equal" in its alert type, Numeric and time properties has extra type as "above" "below" "out of range"
I'm not sure if there's a build-in service for that, here is my solution:
Create a service or subscription or in Expression widget, when CurrentTime - LastUpdateTime > TimeToWait, it will send out alerts and emails
The CurrentTime value is easy to get, and here is 3 possible ways to get LastUpdateTime value:
- Create a TimeStamp property, and each time any property is updated, reset the Time property to current time, the update can be written in other update services
- Use the GetPropertyTime service in Generic Thing Template, and bind it to the name of the property you are concerning about (or the property that's most often be changed), and it will return a time result. This service did not work for Remote Bounded properties, but you could create a new property that get updates from them.

- If the Thing is remote bounded, there would be a isConnected Boolean property, create a Subscription on DataChange event for it

It returns the time when the connection is turned off.