App Name: Stellarium Mobile for Android
Cost: $1.99 USD
Developer: Noctua Software
App Market: Download Page
Stellarium Mobile is a fully-featured planetarium for your phone. It shows a realistic sky in 3D, just like what you see with the naked eye, binoculars or a telescope: it can accurately display stars, planets, nebulae and constellations, as well as landscape and atmosphere for your given time and GPS location.
The sensor control will also enable you to identify what you see in the sky in just a few seconds, just by pointing the phone at it!
Created by two of the original developers of the award-winning Desktop application Stellarium, this mobile version offers most of the functionalities of the original application, with a customized interface adapted for touch screens.