Shen Ji Pan has StarTracker for iPhone 4S (iTunes Link) for the iPhone and iPod Touch in the iTunes App Store for FREE (regularly 4.99) for a limited time.

This is a Star Gazing application which will guide you to recogonize all the bright stars in the night sky! Just hold up and point the phone at the sky to see what stars, constellations and deep sky objects you are looking at in realtime. Full utilization of the build-in gyroscope, digital compass and accelerometer drive the best user experience.