I don't see iPod as primarily an Apple innovation myself. I had (still have) a Creative Nomad Jukebox - OK its clunky and no scroll wheel and not entirely pocketable with poor battery life but its not 'innovation' to fix up those details as technology improves. iPod was a 'me too' variant of the Jukebox - a better user interface sure, but nothing particularly innovative apart from the scroll wheel. I hand it to Apple for the innovation of integration of iPod and iTunes though, that was something no other mp3 player manufacturer managed.
The innovation was not the scroll wheel, but the whole package. For starters, they were the first to manufacture a hard drive small enough to be fitted inside the iPod. Before iPod, the players could hold only about 20 songs in their solid state memory. Overnight, apple introduced a player that could hold .... 1000 songs. That is quite a difference.
Then, they greatly simplified the design, making it usable, for the first time, for a 5 year old. They have also added an excellent program to manage the device (first from Aplle computers, then from Windows based PCs), create playlist, import files etc, and finished that off with the iTunes. It was, basicly, a slum dunk, that have left the whole industry hipnotised.