Ditto on both of the previous comments. The volume control on the factory supplied earbuds act as a shutter release when you using the camera app.
Also, an inexpensive blue-tooth remote shutter release like the Phone skope model is another very worthwhile option. I have used both and have been very pleased with the results. I tend to lean more towards the Blue-tooth option as the earbuds dangling from the Iphone can either get tangled or blow in the wind and thus provide some image shake.
On another related note, I currently have the opportunity to review the Athlon Optics Ares 50 mm spotting scope. It is a deadringer for the Celestron Hummingbird 50 mm model. The optics are nice at the 7.5x setting and up to about 15x. From 15x-22x the optical performance drops notably. Probably good for overall observation purposes but I wouldn't use it for digiscoping above 15x.