Camspace is a PC application (and soon to be Linux and Mac) that allows you to use any object as a game controller through a webcam.
Currently in beta and downloads only available to a select few, the Camspace program loads on your PC and allows you to use any object as a controller for existing and custom-made applications.
Once the application is loaded, you define any bright colored object as a controller, you will need to program the interface to the game or application of your choice to define the mappings.
This is a video of the application interfaced with google earth:
Camspace has alot of interesting potential because of its available APIs that will enable you to create your own applications to interface with random objects around the house. It would be cool to see if fitness items such as barbells, exercise bicycles and such could be fitted with the sensors to enable them to become interactive exercising interfaces to various games on the PC.