It may be too early to say for sure, but Aeris' new heads-up display mask -- the Compu-Mask -- may be the niftiest gimcrack on the show floor.
Containing a miniature LCD panel in the lower right corner of the mask, the mini-computer monitor effectively makes your old wrist- or hose-mounted dive computer obsolete. Capable of showing depth, temperature, cylinder pressure, available bottom-time, and more, the LCD allows you to keep looking straight ahead while simultaneously receiving important information.
When on your face, the LCD readout is very easy to read -- it doesn't obstruct the field of view in the least. When held by the left hand and photographed by the right, however, the readout appears to be a little wonky (see below). If you don't believe me, at least take the word of the bearded gentleman standing near me who shouted, "Cool!" when he held the HUD to his face.
Receiving information wirelessly from the tank cylinder, the mask is air- and Nitrox- compatible; features audible alarms; adjustable backlighting for different underwater scenarios; and uses diver-replaceable batteries.
Expect it to ship in June 2007 and retail for $1500.