I didn't know that the Nexus 7 wifi only model has GPS (it does, right?). I was surprised that Google Maps was navigating and rerouting on my wifi Nexus 7. Does that mean you can download a GPS Navigation app and use navigation even when your device has no connection to wifi? Do you at least need wifi at the outset of the trip so your device or app can look up the address and compute the driving directions or is the GPS functionality able to do that?