the demand isn't there in another sense (lots of people or rich organisations willing to put up money for this).

This pretty much describes most of the innovations I'm personally interested in, where the fruit hangs low enough that twelve-year-olds can pick them, but nothing ever comes of them, presumably because of lack of sufficient market pressures / sufficiently rich and motivated investors.

The concept generalizes, it seems. Are there other (successful) innovations that overcame such hurtles in the past? I don't know where the Rite Brothers got there funding/supplies, for example; I don't know what the astronomy market thought of Galileo's telescope at first / how his spat with the Pope impacted its development; etc. People do seem to be interested in the logistics of spreading useful innovations, at least more so than in my pet game-changers; what sorts of efforts are being made on that front? Givewell's identifying the most efficient charities seems like a good component (why haven't we tiled whole African countries in mosquito nets, yet?), but teleportation would obviously be much better.