Awhile back I was asked to explain marketing. It can be complicated, but the bottom line is finding some application that people are willing to pay for. A classic example is that people do not buy 3/4" drill bits because they want to own one, but because they want to drill 3/4" holes.
For many of us this can be a trial and error process as it is very difficult to predict what people will respond to as they can't often articulate it and may not really know. How many of us enjoy things that were unimagined even a few years ago?
One recently read example was Honda motorcycles, courtesy of Clayton Christensen. The motorcycles were very popular in Japan for making small, local deliveries. Honda had the idea they could be adapted for American highways, but unfortunately the mechanics didn't work out. One of the executives liked to ride his Honda motorcyle up and down country hills in California as kind of a frustration relief. A neighbour wanted to do the same thing and in a short time Honda found a new application as a dirt bike. From there they were able to build up to a wider range of products.
I will be doing a book review of Clayton's book, "The Dilemma of Innovation" and here will just mention some other examples he gives involving disk drivers and steam shovels. In both these cases a few companies had established standards and took on their competition with incremental improvements in what seemed a logical progression. Along came some new products tracking a different direction (smaller size) and naturally were ignored, until new applications led to new markets and eventually new efficiencies that took over the old markets. More on his book: http://www.therealjohndavidson.com/2013/03/the-innovators-dilemma.html
My most personal experience, not nearly as dramatic as Christensen's examples was with a cleaning product. I didn't discover it, nor did the company I represented. When I first became aware of the opportunity I arranged to meet someone at a busy shopping mall kiosk type of table. Time was limited and I was a bit impatient and just asked if they could please give me some literature before I made a decision.
One of the reasons I was impatient was that I was getting headaches after running out of a cleaner for my anti-reflection coated glasses. One of the given testimonials was from an optician who commented that this cleaner when diluted down to being mostly water was superior for cleaning anti- reflection coated glasses. A few years later my boss noticed I was using his product for cleaning my glasses and urging others to try. Without telling me he developed a bi-product for cleaning glasses.
The main target of the cleaner was veterinarians and pet stores for cleaning up pet messes. That eventually led up to another very powerful application which led to another that we had no understanding of. But before then we added the glasses cleaner to our list of veterinary products, mainly just for computer screens. One vet clinic needed to clean its microscope slides immersed in oil as a regular procedure. They found our glass cleaner more effective than anything they had tried. Unfortunately you don't need a lot to keep microscopes slides clean over a year, but certainly establishes a level of credibility.
The other applications we stumbled on from the basic cleaner was for de-skunking and anal discharges (something my boss with his dog had experience with, but had been unable to explain). I couldn't understand the skunking application until I read a book about skunks. Their odour comes through an oil.
Most of these new applications were discovered by customers, not us. A few were discovered by our own trial and error or accidents.
Most products can have a wide variety of applications. We learned an interesting strategy by one of our competitors. Windex we discovered is a fairly good all purpose cleaner (better than the popular all purpose cleaner we used for comparisons), but they must have been smart enough when entering the market to focus on one niche where there was little competition--cleaning windows. They added blue coloring which fit the image they were trying to convey.
It still takes money to turn an idea into a market. One of the first steps is to find a viable application. If you don't have a big budget you can try to make up for it with more effort over more time.