You can add a new monitor in the monitoring section in the app. You can add any metric here that you may want to track and the data will be made available to you in a time-series format across customers. You can potentially add anything that's part of a contract like say,
"Total Invoice Amount", "Amount for a Product", "Free Units Remaining for Product X", "Units utilized for a Product Y".
You can view the corresponding monitor from the list page.