Jupiter Simulator is an astronomy app that shows the location of the four largest Jupiter moons, and the Great Red Spot.
All positions can be shown in real time, or in faster animation. You can set the clock to other times in the future or past.

You can navigate in three dimensions, and zoom in and out. The orbits of the moons can be made visible. You can also predict the next time the great red spot will be visible, and also, search for shadow transits on the planet's disc for each satellite!

Planet and satellites pictures created by Bjorn Jonsson (http://bjj.mmedia.is/) and used with his permission.