all the 3rd party navigation apps will use maps stored locally on the device. I think TomTom has traffic, that would pull from the internet, but I think you can turn that off. I'm going to the states this weekend to do some shopping and pick up my tires, I plan to use TomTom while I'm there.
Navigon will use NO DATA unless you enable traffic. I use it in the US all the time and my data, data roaming etc. is turned off.
Awesome, thanks guys.