plugin for service credits

I am looking for a plugin where a customer can login and can see how many points he can assemble. The process in the plugin should look as follows:

1. the customer receives from us an account with an overview of the total number of points that he has already purchased.(outside the plugin)
2. He can deploy (online) services. these services represent a number of points.
3. while removing or use of these services the points will be deducted from the total number of purchased points.