You need one of these Bad Elf Ipad GPS - Handheld Systems it is a 10HZ device so it is very accurate and doesn't take long to log on at all. You can also power the Ipad off your cigarette lighter with it plugged in to the cigarette lighter socket. It comes with a mini USB lead but you'll need the plug for the socket if you want to run it off your car's system. If you just run it using the IPad's battery, then expect at least five hours. I got four and a half and ended up with 52% battery left but I didn't have the cellular data running and dimmed the screen a bit.
Have just done a trip over to WA ( from Sydney ) the Ipad with Hema app was brilliant,worked all the way we covered some 21,000 klms. Don't worry about a bracket as they are too cumbersome and restrict windscreen view . Buy a suitable protective cover to sit the ipad in ( a book type one with a flap )and use some adhesive Velcro to attach the back of the opening flap to the dashboard so the screen hangs over in front of the radio . It's very visible & out of the way and picks up the satellite signal just fine
Wifi only models=no gps (triangulation only using data network mentioned above - it has no cellular capability so no "mobile" cell network lockdown at all? wifi only lockdown as far as im aware?)
3g/4g models = gps (assisted gps which is real gps but faster - uses wifi/cell signals for rough location if available to speed up the final satellite fix proper location lockdown - can be used accuratly outside of any network coverage)
Further to this confirming the Hema GPS app for the ipad picks up off satellite ( same as normal GPS units on the market ) , so you do not need to be within mobile range to receive like you do to receive / send emails etc . The Hema app is fairly cheap at around $200 for some 90 maps covering all of OZ .. When using the Hema if your doing a long trip you need to have the ipad plugged into your car power supply as it uses lot of power .