FYI, I came across an interesting "fix" for the annoying "accessory connected" lockout screen when connected via USB..

Get the app "NoAccessorySplash" (via Cydia), and it allows you to control the phone when connected. I can confirm this allows for control both via the steering controls / navi and also from the iPhone itself. Album art is now displayed instead of that annoying screen.

Hope this helps someone else who is annoyed by this..