I have found these questions relating to my question, but there has been no development by Google in this area:-
https://groups.google.com/forum/?fromgroups=#!topic/in-app-payments/YFaCBDwaF9g
Does Google Wallet server calls back on every renewal of a subscription?
My question is how does one verify that we should continue providing a service to a customer, if we do not know if they are paying. I don't have time to waste checking manually.
Is this feature available yet?