iPod and iPhone solved problems users had. They needed an easy UI to transition from 12-song CDs to properly tagged 500 track libraries.
The iPhone combined music player, mobile internet device and camera phone in an easy enough to use package for the average cellphone user.
What issue does a headset solve? Apple at least had heavy competition from Blackberry and Nokia back then. Here they are walking in largely unopposed as there aren't enough customers to bother competing over.