Alert configuration for remote values streaming in from the device.

Hello Team,

I have a written a custom email alert service, which gets executed when threshold of a temperature sensor crosses 40.Till here it is fine. Now my requirement is I want to trigger that email service when new property gets added to that thing. 

example: If I have a thing "temperature sensor" and I am monitoring temperature through that in property "temperature".If someone added another property called "humidity"  to that thing then it should trigger the email service and the owner of that thing should get an email saying that new thing called humidity git added to thing "temperature sensor".

Please help me here. How do we achieve this ? 

Thanks in advance