We have a Garmin Nuvi 1450 for turn by turn navigation.
We have installed an iPad running Hema Explorer for moving map display. As it is a Wi-Fi only iPad, a Garmin Glo GPS receiver is used which connects to the iPad via Bluetooth.
The receiver sits on the dash and provides location data to Hema Explorer (and other applications).
The iPad is mounted using a RAM seat mount.
I use the GPS for checking where we are, recording and displaying favourite locations (using waypoints), and for recording our track to be later downloaded into OziExplorer. The Etrex is NOT a navigation GPS unit.