This got me wondering, if the technology to create a virtual laser keyboard exists, why not a virtual projected tablet computer? I started to do some research and found this small UK company which has developed exactly this kind of technology. The company is called Light Blue Optics and the product is "an interactive projector that instantly transforms any flat surface into a touch screen."
Though not yet available to the general public, it is an impressive demonstration of some very interesting technology. You can find more information at the company's website http://lightblueoptics.com/products/light-touch/