Koomus Dashboard K2 Windshield car mount
If you're wary of attaching a magnet to the back of your phone, there is the Koomus Dashboard K2 Windshield mount ($20), which can be securely attached to either your windshield or your dashboard with a 3M Gel pad. If you want to move the mount, just clean the 3M Gel pad in water and reattach it to a different location.
Your smartphone is held by the adjustable holder -- the Koomus is compatible with all smartphones up to 3.27-in. wide. Once secure, you can adjust the Koomus' arm so that your phone is at the desired height and then rotate the phone to your preferred angle. The Koomus comes in both white and black.