Hi,
I have an iphone, but not the 3G so i cant spk for that but the GPS map is google map, i used mine this weekend to get out of trouble in which it did do, but its like a route planner really, and to see where u r, u have to have a phone signal, and have to press the pinpoint buton to find out, so therefore its not really a sat nav, but like i say, it is a great map system.
Hope this helps
Liam