What cloud resources does herokuapp.com cost?

This question is regarding using xbee wifi s6b with herokuapp.com xbee wifi kit. I set up a few button widgets on that website and was able to remotely energize and de-energize relays with my xbee modules with the widgets. Very cool. On the other hand, after a few days, my developer’s account has shown huge amount of resources used, such as messaging etc. Almost everything was through the developer’s limit.

What exact etherios resources does the herokuapp use and how often? Does the xbee use the resources when no herokuapp dashboard is open or only when the dashboard is open in a browser.

Thanks.

As far as I am aware of, it is determined by the configuration of the module and your developer account and not the app.