Your iPhone is already capable of capturing amazing video. With a microphone and lights, you can do even more with it. The Shoulderpod G2 is an iPhone rig with a spring loaded clamp that lets you mount your phone quickly. It also has 6 cold shoes and 2 tripod mounts for all your video gear.
You can use this iPhone video grip to capture video in vertical and horizontal orientation. The G2 weighs only 417g and has a loop for attaching a strap.[where to get it]