It's almost impossible to think of anything that will create a $140 billion business out of nothing."
Lol. Just waiting on the tech. These will all be many-billion dollar businesses: fully immersive 3D entertainment; electric cars; household robots; sex robots; space habitats; real 3D printers (by which I mean they'll be able to print electronics, mechanicals, hydraulics and so on -- able to print any item you can provide the raw materials for. The "3D printers" we have today aren't good for much yet.)
As to what you could do today and have a chance to meet that metric... all I know is it isn't going to be an iWatch class device.
Of course if we were collectively smart we would have "Manhattan project-ed" solar, solar storage, and the means to pass massive amounts of energy around long before now at a similar level, and we'd already be off the middle eastern tit.... but of course that means the big oil cronyism in congress would have to be reined in, and that isn't happening.