A mini description of this since the page doesn't explain it very well: The CarThing is basically a mini Linux device that runs a web app that lets you control your phone's Spotify from the hardware itself. It was designed to be attached to old cars that don't have dedicated media centers.

Spotify discontinued it a while ago and subsequently open-sourced some of the bootloader and kernel code. Researchers then were able to tear it apart, and as a result you can now do whatever you want with it. DeskThing is a project that makes it easier for you to do so; it's basically an app store of custom web apps made by the community that you can upload back into the CarThing.