If you drive and use your smartphone a lot you are asking for trouble and in many states and cities that can actually get you a ticket. You should be using a hands free device for calls and if you use that smartphone for navigation, you probably want a holder of some sort for the phone too.
A new holding clip has surfaced called GoSmart Clip. The thing has a design that should work with any smartphone, though the iPhone is what you see in the company's photos and materials. GoSmart says that the Clip will work with smartphones between 4" to 5" tall and under 0.75" thick. The company does say you need to remove any cases before using it.
The GoSmart clip is designed with a strap that wraps around the top portion of your steering wheel. It has a leather pad that actually sits against your wheel to help keep it from marring your wheel. The biggest problem I see is that the GoSmart Clip will block the speedo and tach on my car and probably on several others as well. You can pick it up in red or black colors for $25.95 and you can get two of them for $39.95. They will ship on December 1.