An interactive projection system, apparatus, and methods for their use are provided. The system includes a projection unit that projects an image of a user interface onto a projection surface. At least one vision sensor is provided that is configured to sense a location of an infrared light source. A computing device that is configured to execute applications to provide the user interface and to determine corresponding outputs based on inputs received by the vision sensor is also provided. An infrared input device, or stylus, is employed by a user to provide infrared light inputs at desired locations with respect to the projected user interface. Additionally, a plurality of styli, each emitting a different respective wavelength of infrared light is also useable to provide multiple simultaneous inputs to the system. An equal plurality of vision sensors may also be employed to separately sense inputs from a respective stylus.