Kemper, Steve. Code Name Ginger: The Story Behind Segway and Dean Kamen's Quest to Invent a New World. Boston: Harvard Business School Press. 2003.
These books chronicle, in highly entertaining fashion, the pains of inventing. Rather than detail each, I'm going to offer observations on both.
First, both books tell the story of dedicated teams who work long hours trying to reach a goal which is something like glory, and something like priority, and not entirely economic -- although everyone hoped to get rich on stock options. As the teams are presented (and if the presentation is accurate) they are the modern expression, I would say, of the impulse that built the pyramids and the cathedrals.
Second, both teams are plagued by problems of the "flexible frame:" they do not know what their users will do with the machines they are creating, they do not know what a "successful" machine looks like, and there is a strongly defined existing infrastructure in which they must fit their contribution.
Third, it doesn't do to sneer at the marketers when they cannot find a market. At least, an investor has to understand what kind of gamble is being presented: "you are investing to change the world, not to make money" probably means at least the latter. In the case of the Eclipse/Eagle, the machine had a market based on earlier customers. In the case of Ginger, the prototype IBOT (unfinished) was created for a potential medical market. But it had no market as yet. Kamen suggested that the Ginger would be the link between cars and walking, and furthermore, replace walking, but - to my eye - the Ginger never had an immediate market (in America). It doesn't address any felt need. For instance, right now, when I run errands, my car carries me and my packages together. My errands range about 1-20 miles on a daily basis. The Ginger only hauls people, not stuff, and it wouldn't be comfortable for more than 1 or 2 miles. There are relatively few local bag-less errands that fit this profile. All of which does not mean that the Ginger cannot create a market for itself, but certainly it will take some time for users to create uses.
Finally, there is something of a picaresque pirate mythology to these books: the scene is a broad canvas - on strut the young guns, the smart guys, the wild-eyed inventors, the steely-cool leaders, salesmen, hucksters and barkers. It's fun, even if it's not true.