When it comes to mp3 players, there is hardly any competition. The iPod rules them all. It doesn’t matter if someone else can build a batter mp3 player at this point in the game, Apple owns this category.
In the realm of e-readers, there have been a few different players. There’s the Nook and I think Sony has a model or two while Apple has completely stayed clear of e-reader only devices. There has been some competition between the Apple iPad and Amazon’s Kindle, but there have hardly been any sparks. They are simply two different kinds of devices.
Just has Apple dominates the mp3 market, Amazon is about to seal the deal and put the final nail in the coffin of competition and rule the e-reader market with their next move.