Segway seems to have hardly been a dead end, or useless for that matter. Segway-style devices like the electric unicycle and many other light mobility devices seem to be direct descendants of the Segway. Segway introduced gyroscopes to the popular tech imagination, at least in my lifetime (not sure before).

What other light mobility devices? E-bikes and scooters seem to be the big things and they’re not anything like a Segway descendant.

A world where Segway never happened would be nearly indistinguishable from our own.

Smartphones introduced gyroscopes to popular tech (and no, people were imagining them before transistors), Segway had nothing to do with that.