Develop a Mac Application

I would like to create a piece of Software, which allows allows user defined actions to be performed based on conditional inputs. Consider https://ifttt.com. It automates actions based on inputs from multiple sources (twitter, Facebook etc). I would like a similar but much simpler version as a Desktop App. Simpler because it only needs to use one input (A Pusher Stream), and only need to perform one type of action (POST /GET) Requests.