Psst Sports Fans: Want a Singing Shirt With Optional A/C?

GREG ROSENWALD is showing off.

He zooms around a small asphalt parking lot on a one-wheeled contraption that sounds like a motorcycle and starts like a lawn mower. The motorized unicycle-looking device propels him from behind as he grips the handlebars to steer and brake.

His back rests in a ''V-shape'' made by the handle bars; there is no seat. On his feet are roller skates, which he sometimes interchanges with a skateboard.

Mr. Rosenwald hopes his invention, called the Roller Cycle, will become as popular as in-line skates have in the last several years. And he's doing his best to promote his product - with a retail price of about $650 - to hordes of enthusiastic and skeptical buyers.

''You hold your hand like this, and you go 'vroom, vroom,' '' he says, speeding away from the crowd.

Welcome to the wide - and sometimes wacky - world of sports, where the meaning of ''athletic activity'' seems to be constantly stretched. To find usual and unusual gadgets and goods, buyers from around the globe come here for a few days each February. Billed as the largest sporting-goods show in the world, the Super Show draws more than 100,000 industry folks who gawk, stalk, and balk at the array of athletic equipment.

More than 1,200 exhibitors and 3,000 manufacturers take over the Georgia World Congress Center here each year. Long lines wind down even longer halls as people wait for autographs from sports celebs such as Kareem Abdul-Jabbar and Nadia Comaneci.

While much of the show displays more traditional merchandise, such as balls, rackets, and paddles, there are also more quirky products for sale. A sampling:

* Shirts that sing. Say you want to demonstrate you're a diehard fan at your alma mater football game. Michigan-based Sound Around Ltd. sells a line of T-shirts, sweatshirts, and hats that will play your school fight song at the touch of a button.

* Personal air conditioners. You're breaking a sweat playing your favorite sport or baking under the sun as a spectator. Misty Mate Inc. from Arizona says it has the answer: a cylinder filled with cool water worn like a belt. An attached sprayer mists the air with a fine spray that is said to reduce temperatures by 30 degrees temporarily. Less than $40, it weighs two pounds and requires no batteries, says Rich Donahoe, the company's national accounts manager, who aims the sprayer at people passing by his booth.

* Self-erecting tents. Created for those who like camping but not setting up the campground. The tents, designed by Arizona-based Outdoor Innovations, look like flat discs. ''You throw it up in the air like a frisbee and give it a spin,'' says the salesman, and in a matter of seconds the tent is ready. Retail price: from $50 to $350.

* Mitt breakers. Softening up a baseball glove can take six months; now it takes as little as three days, says Richard Greene, president of Pocket Shaper, manufactured in Connecticut. The invention, designed by his teenage son, is a hard plastic bat with a ball attached. Slamming it into the glove several hundred times - done while watching TV, he suggests, will make the glove as pliable as if it had been used for a year. Price: $12.95.

The products draw mixed reactions. ''It's very strange,'' says Jose Negrette, who owns a sporting goods store in Venezuela, of the Roller Cycle. ''It defeats the purpose of roller skating. It's more like a motorcycle.''