If you do rely on your gadget for following directions, it's safer to have it mounted somewhere in the car.
If you heavily rely on your smartphone for directions or need to access it to make calls over Bluetooth, then you'll want the phone mounted somewhere at eye level. The windshield is a good place to start.
CNET editors recommend the Parrot MiniKit Smart. For one hundred bucks, this device will securely hold your phone, charge it and provide Bluetooth speaker phone capabilities. It is heavy, so you'll want to make sure that suction cup is secure.
If the windshield mount obstructs your sightline or is too far away from you, try mounting your smartphone to your dashboard. CNET recommends the Brackertron MobileDock for $30. It doesn't do much more than cradle your phone, but its sticky mounting mechanism is sure to work on all hard surfaces.
If those devices fail, be sure to invest in a mapping app that gives you good voice instructions on where to turn...in case that phone does fall under the seat.
(Kara Tsuboi, CNET.com for CBS News)