An application that displays a number and a button. The number increases when the button is clicked. This app proves that you can have data stored in properties on your Activity class and manipulate the data inside a method bound to a click listener.
An app that displays an Image, a paragraph (at least) of text, a next button and a previous button. The app allows users to cycle through images and read summary descriptions. Pressing next goes to the next image and it's description, pressing prev goes back. The app displays and indicator so users know how many items are in the list.