Was checking out Autoblog and they had a story and link to this:
Nissan offers top-quality navigation system for low price | detnews.com | The Detroit News
$400 option Nav equipped head unit with USB connectivity on the Sentra and possibly other "high volume" models.
I doub't they would offer it on the Z as it would pretty much negate the option on the touring model but it would be nice on a Nismo or base for that price.