I use an old 1st Generation iPod nano to play music in my car. I hook it up via the dock connector.
I noticed that when it's hooked up to my car stereo via the dock connector, I'm locked out of the user interface: the screen doesn't show anything about the song being played, I can't pause or fast-forward or play from the iPod's buttons, and I can't navigate to select another album and start playing it.
In contrast, when using the iPod to play music through headphones (not connected to my car), I can play a song. While the song is playing, I can navigate through my other albums, select a new album, and press play on the other album to switch to that one. But I can't do this when it is connected to my car.
I don't have this problem with an iPhone 4: even with the iPhone 4 connected to the car stereo via dock connector, I can pause playback or navigate to another album and start playing it from the phone's touchscreen.
Is this problem specific to the 1st Generation iPod nano? Will other, newer iPod nanos have the same problem? Will all iPods have this problem, including the iPod touch and iPod shuffle? How can I identify which devices will or won't have this problem, short of buying it and trying it out?
(I don't want to use a 1/8" to 1/8" cable via the headphone jack, or a FM transmitter.)