I currently work on building an open PCB for translating Android headphone remote signaling to Apple remote signaling resuming the awesome work of David Carne[1].

Basically it is a circuit where you could use any Android inear Headphone with remote buttons on any Apple device with Audio Jack - a TRRS Plug - TRRS Jack translation layer between the 220Ω/660Ω vol+ and vol- signaling on Android to the proprietary Apple ultrasonic chirp protocol.

Probably nobody (besides me) will ever require this, because everyone just uses Bluetooth these days and noone else uses the iPod Nano 7g :-)

1: https://tinymicros.com/wiki/Apple_iPod_Remote_Protocol