Usually when presenting a slideshow you have to either have a handheld device to switch slides or be near the computer to use the mouse / keyboard. Maybe you also have a laser pointer to highlight things on the screen.
Wouldn't it be nice if you could use gestures to switch slides or to zoom? Or you could just point with a finger at the screen and the slideshow program would highlight the area you point at.
Last Friday I bought myself a Kinect Sensor and connected it to my PC (here is a tutorial how to do that with OpenNI).
Below is a screen capture of my first integration into Candescent Slideshows. Currently you can either go to the next slide if you move the hand (or anything else) from right to left or go to the previous slide by moving from left to right. The image is mirrored, because the Kinect is located in front of me.