HRoth - 2:49 pm on Oct 29, 2011 (gmt 0)
One of the groups of products I sell fits all of these exactly except "low dominance of existing competitors." The way I have gotten around that is to find/create a subniche. This group of products is what I expect to keep on selling indefinitely. They are all those things on your great list and for me, fun and interesting too.
One thing I think is ideal is the capacity to produce the widget yourself with little investment of materials or property, mostly just skill. Skill makes it difficult for others to make, and you don't have to worry much about the supply route or variations in currency when you make it yourself.
I think the idea of it being small and light is excellent and key for the future of increasing energy costs. Cool list!