How to use custom back end model with Genie MVC app?

I am trying to use Genie to create a MVC structured web application, but I have not figured out how to include something other than a database retrieval system for the model.

I have read the entire documentation and the standard procedure seems to connect the controller to a database which serves as the model via searchlight. However, I have implemented my own custom model which does calculations rather than simple database retrieval, and then returns its desired output.

What is the proper way to include a totally custom model in a Genie MVC application?

Which directory should it go in and how can I connect it to the controller?