I think it is the way an item is marketted as to which category it falls in, but it also has to make life easier, even if only for one specific purpose, and also be able to take the place of something else you already have. I think there is a lot of overlapping areas.
I don't consider that hand-hammered wok of the eighties as a gadget, but it was certainly marketted like one. It's a wok, which is different than a fry pan and basically has its own use and place in cooking.
consider the GF grill as a gadget. It was marketted like one and it doesn't do anything differently than a stovetop grill or even outdoor grill, except cook on both sides at the same time. Why do we need that? And what do I care if the grease drips into a tray? The food isn't cooking in grease on either of the other two items I mentioned. I had one and gave it away, then my parents brought me over theirs one day, and I gave that one away, too, then my sister asked me if I wanted hers.... The novelty had worn off and we all went back to our original methods of cooking and grilling. That, while a gadget to me and those I personally know, is obviously not a gadget to some of you who actually used your more than a couple months.
That stick blender I just ordered; I don't consider that a gadget because I do not have a food processor or a mixer and I don't know where my blender is, so lets say I don't have one of those either. It is going to be a useful tool...... Until that time when I do have a FP and a mixer and I find it easier to leave the stick blender sitting in the drawer. And there was quit a few infomercials out on these a while back, so I think it could easily fall into the gadget category if I let it.
Hmmm, food saver vs handi-vac.... I don't even want to touch that one. I use my handi-vac all the time and my FS collects dust, but if you were looking at both of them side by side, you'd almost have to say the handi-vac was the gadget.
Hey GB, what about that pot that does nothing but boil water?