Not sure about iPad II, but on iPad I, you need the 3G version for GPS. (built in antennae)
Foreflight HD or WingX Pro give you moving map (I have both), plus Wx, airport directory, flight planning, etc. etc.
There are a few iPad Kneeboard mounts available, though I'd be careful about relying on it as sole source of navigation for a few reasons, one being impact of light and sunglasses on visibility.
I've used it on two flights as a secondary source and it was useful, though both were two pilot situations so I did not have to worry about fiddling with the iPad and the controls at the same time.