On top of the hardware and algorithms, Bell says, Reactrix is also thinking about the best design for the user interface. As with touch-screen technology, gesture-based interactions have been toyed around with before, but it's still unclear what sort of interface would work best for most people. There are a few interactions that lend themselves well to a gesture interface, such as a boxing game or sliding pictures across a screen. However, engineers still haven't figured out the best way for people to interact with a virtual button, for instance. It may seem trivial, but it's unclear how to press a button when there's nothing to touch. "There's an exciting opportunity here to create the standard gestural interaction with displays," says Bell. "We want to be at the forefront of creating that."

Regarding the forthcoming Hilton displays, Bell says he expects that travelers will be able to play games that relate to local attractions and navigate menus for more information. In this way, he says, people have fun interacting with advertisements, instead of just passively flipping through a brochure.

With its floor displays already available in U.S. shopping centers, "Reactrix has proven the value of interactive marketing solutions for use in public spaces and, specifically, in use with crowds, for which it is difficult to track individual people's body movements," says Michel Tombroff, CEO of Softkinetic. He suspects that the market for gesture-based technology will grow in the coming years, thanks in part to the falling price of 3-D cameras.

The engineers who build these cameras and computer vision systems have made great strides in recent years, says Scott Klemmer, a computer-science professor at Stanford University. "Cheap cameras and sensing [systems] are going to usher in a new genre of user interfaces," he says.

Bell says that the falling price and shrinking size of these cameras is one of the main reasons that his company partnered with Samsung. The display company, he says, should be able to find a compact and cost-effective way to integrate the camera technologies, Reactrix processors, and algorithms into commercial displays that can have a home outside a Hilton hotel lobby.