With Co-Pilot once the app is installed along with the desired maps no network connection is needed unless you want additional features such as traffic info. For mounting I use a tablet mount that fits into a cup holder. My tablet is a Samsung Galaxy 4 7" which cost $158 and the mount was $29.99. App was free. Both have come down in price over time.
I like Apple based products but for this application an iPad didn't fit my needs. The problem was only the iPad with cellular capabilities have GPS and I would rather not add an additional device to my service.
Amazon Samsung TabletTablet Mount