worth a look? I love the Nissan Satnav system great direction and really easy to use and follow but it's stuck in the front of my car. So i'm looking at a portable system is the iPhone or Nokia N95 any good at direction finding. Does it need any other addons to work and do you need to subscribe to expensive pay services to use it or is it preinstalled on the phone. And does it need a telephone signal / network coverage to work the mapping.