Ever been to the Haunted Mansion at Disneyland and found yourself surrounded by ghosts? The technique behind it can now be held in the palm of your hand.
Less a hack than an imaginative kludge, media artist Jitsuro Mase took a classic optical illusion known as "Pepper's Ghost" and scaled it down to iPhone size. Basically, a series of mirrors and careful lighting techniques make three-dimensional objects appear in mid-air.
Mase's gizmo isn't ready for prime time yet (it was created for an Austrian expo and requires custom content to optimize the illusion), but this video gives you an idea of how it works: