There's at least two ways to design a new category of product:
1) Invent a new technology and incorporate it into your design (the Dyson Vacuum), or
2) Design something around a novel use of an existing technology (the iPod).
Both types can be exciting, but what we like about 2) is that you don't have to spend a dime on R&D vis-a-vis the technology.
Let's take vacuum technology, for instance. Not the Dyson cyclonic stuff, we're talking regular, run-of-the-mill suckage from an air pump. In 1901 a Brit named Hubert Cecil Booth patented the first powered vacuum cleaner. Check out his "research" (courtesy of Wikipedia):
[Booth] noticed a device used in trains that blew dust off the chairs, and thought it would be much more useful to have one that sucked dust. He tested the idea by laying a handkerchief on the seat of a dinner chair, putting his mouth to the handkerchief, and then trying to suck up as much dust as he could onto the handkerchief. Upon seeing the dust and dirt collected on the underside of the handkerchief he realized the idea could work.
Although Booth lost the consumer market to Hoover--Booth was apparently the HD DVD to Hoover's Blu-Ray back then--he built a good business producing industrial-sized vacuums, and his company (renamed Quirepace) still exists to this day--and now they make Pneumatic Tube Transport systems, another cool use for vacuum technology.
But back to regular household vacuums. They evolved through various form factors throughout the 20th century--standing up, lying down, shrinking to fit your hand--before detouring into Dyson's cyclonic separation and even into semi-autonomous robot form with the Roomba.
But the purpose was always the same: To clean dust off of floors (at least until the 1970s, when it was used to suck spilled cocaine out of the shag).
Then someone (we don't know who, but judging from the photo below, it was someone from the early 1980s) got clever and saw another use for vacuuming technology: Clothes storage.
The leap from cleaning floors to making sweaters smaller is not at all intuitive, but the concept was sound and now the market is rife with vacuuming storage systems for clothes.
The latest iteration of this idea is aimed at, of all people, hunters and campers. The idea is that after slaughtering fish or little furry animals or what have you, you seal them up in a Zip Vac bag, keeping the kill fresh for the ride back home.
And there you have it. So, take a look at some of the technology we've got lying around, and ask yourself: What else might that be good for?