Slightly shifting the topic, I have a hard time figuring out why manufacturers of add-on products that use FM modulation don't add some sort of RDS output for their products. An add-on CD changer could display the track number and time, or CD Text information. An XM tuner could display the song name.

This wouldn't obviate the need for a separate display unit for those who don't have RDS radios, and you'd still need external controls. However, it would really increase people's install options.