A nice live wallpaper showing a transulcent cube of 3D Perlin noise.
This simple app shows details of the moon & suns status for a given position on the planet and time & date.
The calcutations for the moon are made using the CalcEphem code taken from the web. The graphics display shows the current position and phase, as if you were looking up at the sky (hence east and west are reversed).
The sun rise & set times are determined by the "sunset type", ie the various ways in which "sunset" is determined, ie when the sun crosses the horizon, or when it gets too dark to read.
Switch on GPS and you can use that for your location, otherwise you need to enter a place and lat/long (east is positive) from the menus.
The red line is a compass needle pointing north.