Here's one that gets filed under "Why the hell haven't they done that yet"--the invisible camera flash. Anyone who's ever been temporarily blinded by an obnoxious aunt in an attempt to photo-logue every moment of every event for later enjoyment can appreciate the notion of an invisible flash, as can anyone who's ever been the photographic victim of crimson eyes or white spots that result from a traditional flash.
Researchers at NYU are currently working on a project entitled "Dark Flash Photography" that would eliminate the traditional light-based flash in favor of one that uses light that we can't see: UV and infrared. The camera takes two rapid-fire pictures for each photo: one monochrome picture with the IR/UV light and then one flashless picture that relies solely on ambient light. Software then combines these two photos together, using the monochrome image to provide detail to the otherwise fuzzy ambient light picture. The result is one photo that looks as crisp and clean as a photo taken with a conventional camera--only your eyes are actually open and hazel.
The invisible flash will be capable of working with traditional camera equipment and appears quite easy to integrate with existing technology. The only shortcoming is that because it requires two pictures to work, it cannot be combined with multi-shot cameras to create an action sequence. The Dark Flash will be displayed at SIGGRAPH 2009 and hopefully on the next camera that takes your picture.
NYU via Oh Gizmo!