How to automatically close an OS X apps after not being used for a number of minutes?

How to automatically close an OS X apps after not being used for a number of minutes??

I am looking for a way to auto-close apps that are not used (focused at least) for a number of minutes, a number of minutes configured for each one.

Why? While freeing up memory is not so important in my case, decluttering the number of opened windows on OS X it is.

I am currently using ControlPlane to automate starting or stopping of apps based on different profiles and if there is a way to extend it to do that too it would be great.

You could use Quitter by Marco Arment: https://marco.org/apps

I believe that OSX does this automatically, via AppNap. You don't need to pay a third party company for this feature, since Lion.