The Kepler space telescope is a NASA mission to detect Earth-like planets. This app is maintained by a professional astronomer and keeps you up to date will all publicly released exoplanet candidates. You receive a push notification whenever a new dataset is released.

The app visualizes the discovery method, orbital parameters and sizes of all planet candidates. It provides background information on the Kepler spacecraft and exoplanets in general.

An interactive three dimensional visualization of the milky-way lets you re-discover every candidate in Kepler's field of view. You can zoom in from the edge of the solar system to the Kepler stars and watch the planets revolve around them.

Also try the free Exoplanet app for iPhone/iPad which lists all confirmed extrasolar planets.