This Android app lets you classify Galaxy Zoo subjects. It is available in the Google Play Store: https://play.google.com/store/apps/details?id=com.murrayc.galaxyzoo.app . Try beta versions early here: https://play.google.com/apps/testing/com.murrayc.galaxyzoo.app . See also the iPhone app for Galaxy Zoo: https://github.com/murraycu/ios-galaxyzoo/