Sophie's iPod is one of the only things Sophie Foster brought with her to the Lost Cities from the human world. Before the events of the series, she would commonly use her iPod to drown out the human thoughts that crowded her brain by listening to music.
History[]
Book 1: Keeper of the Lost Cities[]
After bringing her iPod to the Lost Cities, it runs out of battery due to the lack of power outlets. But when Dex visits Sophie at Havenfield, he picks up her iPod, and upon discovering that it is dead, tells her that he can make it solar powered. When he returns it to her as a Midterms gift, it has a small green rectangle set into the back, and he tells her that it is now solar powered, and he had added a speaker. Sophie responds by saying that it was the best gift he could have ever given her. This is likely meant to serve as foreshadowing for the reveal that Dex is a Technopath near the end of the first book. When Sophie discovers Grady and Edaline canceled her adoption, she uses her iPod to put on her "angry" playlist.
Book 3: Everblaze[]
In Everblaze, Sophie asks Dex if he could connect her iPod to the internet, and he adds a receiver in the shape of a small silver triangle that sticks out of the base. He gives Sophie her iPod back during Magnate Leto's inauguration as Foxfire Principal. Later, Sophie uses it to search images of Green Boots Cave so as to teleport to that location.
Book 6: Nightfall[]
It was revealed in Nightfall that Dex was planning to give her crush cuffs before wimping out and giving her the iPod instead.