You have to connect the handbrake wire to ground, afaik. Thats what i did on my 8400 and this will bypass the handbrake, so you can use alle Features of the Radio also while driving.
But at least in Germany its Not allowed to do this, but who Cares?
@mike: i just noticed that it seems that the landscape lock is still active after closing the appradio app. For example Mail App. and Safari stay in landscape no matter whats the iPhone orientation.
Dont know if you already have this on your buglist.