I've just come across this app today - available on Android and also iOS devices (iPhone, iPad etc) too.
It is a pretty simple app with a pretty simple goal: A step by step guide to prayer and its precursors.
Prayer is something where many can feel embarrassed to ask questions as they think they should already know everything, so having an app that covers the basics is a very useful thing.
This app covers all the basics wudu, ghusl, prayer, funeral funeral (something that can be performed so occasionaly that you need to brush up every time before any funeral you attend), eid prayers and salaatul tasbih.
How do we know which direction we should face when we pray?
There are ways of calculating this - you need to know your current location, the location of the qiblah and also some way to determine direction.
Most android phones have built in GPS (and most/others can also use other means to determine a good approximate of the location), and a built in compass. This should be enough for some app to combine the data and let you know which direction to face.
I am not the first with that realisation - there are a few apps on the Angroid Marketplace which say they can locate the qiblah/direction to face when praying. I tested the free options.