Here's something todo with your GPS.    Use your home co-ordinates to make a nice sundial for your garden or an outside wall...

Those sundials you buy from the garden centre don't factor where you are in the world.  So I've found a nice bit of software that dows all this for you.

Quote from the Sun Shadows website -

This software does all the calculations to allow you to build a wall mounted dial for a wall that faces up to 60 degrees away from due South.  It takes into account your latitude and longitude to provide you with a highly accurate and unique timepiece.  It is not possible to design a more accurate sundial.

http://www.sunshadow.co.uk/index.html