Moving Shots
But you want moving shots with your iPhone so you’re just going to hand hold it. You have a pretty steady hand, right?
When hand holding your iPhone, there is far too much side to side movement when shooting even if you think you’re holding it really steady with both hands. It may be okay for a few seconds of footage but if you want something people will watch, you have to steady that shot.
Zacuto
Zacuto, the leading indie camera accessories maker in the professional market has some options you’ll want to check out for hand held shooting and iPhone stabilizers. All work with the iPhone 3G, 3Gs and iPhone 4.
Zgrip iPhone PRO is a completely adjustable, quick releasable handgrip system for shooting professional stable video using the iPhone.
The iPhone snaps into the iPhone cradle, the cradle snaps into the Zacuto Zgrip and voila! you are ready to shoot. The handgrip fully articulates, and all of the red levers allow you to adjust every angle to get those interesting creative smooth shots.
You can add some cool accessories to help you shoot better sound, lighting & for getting those cool high angles. They also have a tripod mount you can add so you can quickly go from your Zgrip iPhone to tripod in seconds, if you so wish.

Zgrip iPhone Jr.