As part of the process for making Wired, I worked with some students over the summer to create a load of gameplay prototypes.
Nearly all of these games took one person 2 weeks to make (though a couple took longer). They all have something interesting about them and are also all flawed to some extent. However, each prototype showed enough to know whether the core idea would work and where the potential risks lay.
I worked on a number of camera-based games for Playstation during my ten years at Sony.
This video demonstrate the book tracker my team developed. The player holds a real cardboard book in their hands while the PlayStation camera looks at them. On the TV, the book is transformed into a magic spell book. There are a number of systems working together to pull off the illusion including: Book tracking, hand segmentation, PS Move controller tracking and motion detection. Note that the PSEye camera is a fairly standard web camera and doesn’t have a depth sensor.
In this link you can see an overview presentation of how the book tracker part worked. The photos in the presentation show Tom Lucas-Woodley, one of the senior engineers who poured his soul into this to get it working: book-tracking_reduced.pdf
You can see adverts for the actual products the technology went into here: