The developer of SpiralCam contacted me to let me (Mike Weasner)know about this app for iPhone Deep Sky Astrophotography.
The app uses long exposure and automatically does star finding, registration, tracking, and stacking on the
iPhone. After testing SpiralCam for awhile I discovered two other apps by the same developer: MilkyCam
and SaturnCam. MilkyCam is similar to SpiralCam except its focus is sky astrophotography.
SaturnCam is a much needed iPhone app for imaging planets using video and it will stack the video frames on the iPhone.