[Ezra]

According to this:
Disney invents interactive 3-D projection system
Disney applied for a patent for a system that might be used for Midway Madness. The device could be anything that shines a light or tracking beam. It could be a pair of glasses, or a hat. Or it could be a flashlight that the guest could shine on surfaces to reveal 3D characters that would react in some way. I think something hand-held and mounted in the vehicle would be more practical than a hat or glasses, but who knows? The patent may have nothing to do with Midway Madness.