The sPot takes a fourth-generation iPod and converts into a Spotify streamer. Using a Raspberry Pi Zero W, the sPot offers built-in Bluetooth and Wi-Fi while retaining the iPod's iconic click wheel. The sPot should cost around US$100 to create.
https://www.notebookcheck.net/Raspberry-Pi-Transform-the-popular-single-board-computer-into-an-iPod-that-supports-Spotify.519394.0.html