Once seen as the future, these products turned out to be flops. 

From electric pedal cycles to 3D TVs, read on to see the innovations that never managed mainstream success, and just why they failed.

Smell-O-Vision inventor Hans Laube thought his method of releasing odors into a movie theater auditorium so that the audience could smell what was happening on screen would be adopted by cinemas worldwide when it launched simultaneously in New York, Chicago and Los Angeles in 1960.

It wasn't meant to be. Movie-goers complained about a hissing noise when the aromas were released and commented that the smells were out of sync with the movie. Along with a similar innovation called AromaRama, Smell-O-Vision was swiftly abandoned and consigned to the history books.

The early precursors of these James Bond-worthy vehicles were developed in the 1900s, and a commercial model, the Amphicar, was launched in 1961. Almost 4,000 were produced from 1961 to 1965, but the Amphicar was never the huge success it might have been.

As one owner put it, the vehicle was neither a good car nor a good boat. These days, Gibbs manufactures an amphibious car called the Aquada, but the technology remains niche and prohibitively expensive for most people.

Years later, another vehicle that was set to transform our daily lives hit the market. The battery-powered one-person Sinclair C5 pedal cycle was unveiled in January 1985 by British inventor Sir Clive Sinclair at Alexandra Palace in London, but the vehicle was mocked from the get-go.

After some of the vehicles failed to work during the launch event, the British press savaged the Sinclair C5 and sales fell well below expectations. Deeply indebted, Sinclair ceased production of his eponymous vehicle later that year, and the remaining models were sold off at a knockdown price.

Ever since LG launched the world's first model in 2000, the futuristic-sounding Internet Digital DIOS, state-of-the-art smart refrigerators have became a stalwart of trade shows almost to the point of becoming a long-standing joke, yet sales have been modest to say the least.

Dubbed 'intellifridges', these connected appliances can order food online, suggest recipes and store notes. The thing is, few people have been prepared to part with up to $20,000 to get their hands on one, especially since their PC or smartphone can do pretty much everything the fridge's inbuilt computer can.

Back in 1940, Henry Ford predicted a mass market flying car would be inevitable, but the concept has never got off the ground, and every attempt to invent a viable model has fallen flat and ended in failure.

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Early models such as the Aerocar never made it past the drawing board and recent inventions like the I-Tec Maverick (pictured) have failed to attract legions of buyers. Be that as it may, Ford's prediction may well come true in a slightly different form in the not too distant future. Several carmakers are developing passenger drones right now that could revolutionize the way we get around.

The most infamous incarnation of the self-balancing scooter was launched in 2001 to a frenzy of publicity. The Segway PT was touted as being “more important than the internet” by venture capitalist John Doerr, and even the late Steve Jobs said the vehicle was “as big a deal as the PC.”

Sadly, the Segway PT was never a game-changer and, apart from minor success as a vehicle tourists hire for sightseeing or security guards use to patrol shopping malls, the self-balancing scooter has been a turkey. In 2020, it was announced that no more Segway PTs would be made.

Sony's Blu-ray technology was up against rival Toshiba's HD DVD in the mid- to late-2000s, with both vying to be the go-to format for storing high-definition video and audio.

Sony won the war by including a Blu-ray player in the PlayStation 3, ensuring a huge market for the technology. Toshiba threw in the towel and stopped developing HDTV in 2008, ceding the market to its competitor. 

3D TV was supposed to transform our living rooms into spectacular 3D movie theaters. Following the release of the movie Avatar in 2009, TV manufacturers were falling over themselves to embrace the innovation and build 3D functionality into their sets.

Marketed as the future of home entertainment, 3D TV flopped. Besides a lack of content, people just weren't into wearing bulky pairs of glasses and risking a headache to watch TV. Demand plummeted, and LG and Sony, the last two firms supporting the format, stopped making compatible sets in 2017.

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Now take a look at some accidental inventions that made a fortune