Apple TV + iPhone = Ultimate geeky car audio system
www.appletvhacks.net/2008/08/30/apple-tv-iphone-ultimate-geeky-car-audio-system
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
If you ever wanted to prove your geek-cred to your friends what could be better than using your iPhone as a graphical remote for your car stereo.
Nels Johnson has done exactly that, and has posted the details for how to do it yourself at his site http://www.quickanddirty.tv/.
We’d point out that you should probably have someone else controlling the tunes, whilst you pay attention to the road!