In his blog Xavier Gouchet talks about a really nice application example that will be shown at Laval Virtual in april : an AR pool game !
Authors: Samuel Jordan, Michael Greenspan
Abstract: ARPool is an augmented reality system designed to assist shot planning and execution in a game of billiards. Using a projector-camera combination, ARPool is capable of detecting the ID and location of each ball on the table, as well as tracking the position and orientation of the pool cue in real-time. This information is fed through a custom pool physics simulator to obtain a complete table-state timeline of the shot. The shot data is dynamically rendered in real-time directly on the surface of the table using 2D graphics.
A useful, practical, usable (sellable?) tool if you ask me !