LiveView Screencaster is a free mobile application design and prototyping tool by Nicholas Zambetti. The application allows you to visualize your artboard and interact with your mobile application prototypes. You would need to download both the LiveView for Mac, and LiveView for iOS applications. In order to use the application, the devices you use have to be able to communicate with each other via same wireless network.
I have included some screenshots below that show you what to expect once you download the application(s).
The images above represent the mobile application view upon launch. The left side shows the application screen before a connection has been made with the desktop application, and the one on the right shows that the connection has been made.
The image above shows the desktop application finding the mobile application on the network.
The image above shows the mobile application and desktop application are connected. The light rectangle visible around the network browser indicates the mobile screen area.