(FORTUNE Small Business) – You may say I'm a dreamer, but who the heck isn't? We all experience moments of clarity when a perfect product idea pops into our head. Yet the sad truth is that none of my brainchildren have launched a business. We still live in a world where you can't monogram toast or even buy spray-on socks.

But then, some products are just too useful to see the light of day. Ever sit under a 20,000-hour electric light bulb? Me neither. Although the technology has existed for years, manufacturers make a lot of money selling bulbs that must be replaced after a few hundred hours in service (sooner if you've installed them in hard-to-reach locations). As a result, the eternal bulb's commercial prospects remain dim. German highways have long been built using materials that require far less frequent repairs than their U.S. counterparts, but U.S. paving contractors prefer methods that make more work for them and their teams of guys leaning on shovels staring at potholes and blocking traffic. Or so I've read.

I don't mean to sound like a conspiracy theorist. I'll leave that to the frustrated inventor of SafetyPIN, ingenious software that lets an ATM user summon police by keying in his PIN backward. "Most of my problem is that I'm dealing with brain-dead zombies from planet Gloxor," says Joseph Zingher, referring to banking execs. (Later he implores me to "not make it sound as if I'm bashing anybody.")

Zingher, 47, has spent so much money pushing his invention that he is now broke, he says, and has been forced to move in with his brother in Beach Park, Ill. He describes himself as "an obsessed old man." Zingher dreamed up SafetyPIN more than a decade ago but has yet to see a financial institution install the software. "They know customers are scared of ATM crime, so the banks don't want to talk about the problem," he says. "They don't want their customers to stop using ATMs. I am dealing with immensely powerful people who are in denial." (Not so, counters Thomas Kelly, a spokesman for Chase, the consumer unit of J.P. Morgan Chase in Chicago. "When they are at an ATM," says Kelly, "we advise our customers to be aware of their surroundings and use commonsense caution.")

Or consider Boston-based shoe designer Hank Miller, whose design for a shoe that expands with a child's growing foot provoked open hostility from the footwear industry. One department store buyer even accused Miller, 46, of trying to "ruin the kids' shoe business," he says.

Miller's shoes, called Inchworms, expand one full size in half-size increments when wearers press a button on the side. Introduced in 2002, the shoes could lead parents to buy footgear less often. That, says Miller, is why shoe stores won't stock his products. "Retailers hate me because they feel very threatened by me," he says.

L.L. Bean briefly carried Inchworm shoes at its flagship store in Freeport, Maine. "If I had stayed, I probably could have gotten them into the catalog," says Barbara Barvoets, 44, a former senior product-line manager for kids' footwear at L.L. Bean. "Retailers haven't taken the time to understand Inchworm. It's not the only shoe a kid will have--it is not a sneaker or a dress shoe, just a casual slip-on--but it fills one niche."

For now, Miller has licensed the brand to an Italian footwear company and has set up a website to sell the shoes. "We're not where I'd like us to be," he says, "but we're selling a fair amount."

Fellow maverick Nugent Vitallo hasn't even made it that far. Vitallo invented a shirt with the breast pocket stitched inside it, freeing wearers to lean over without losing pens, iPods, and other pocketware. (He got the idea after a dangerous encounter between one of his children and a falling pen.) Late last year, having been shunned by retailers, Vitallo spent $60,000 on print ads--only to be ignored by consumers. "Someone doesn't want me to get the kind of response I should be getting," says Vitallo, 60. "Maybe the folks who make eyeglasses don't like the concept because people won't be dropping and losing their glasses so much." He's joking--I think.

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