What if you have a great idea in the Bathroom or Kitchen and you don't have pen and paper close by. If you have a window or mirror you can use the pen to write down your ideas, or recipes. Or maybe you want to may a diagram on large white board but your at home and you don't own a white board well, you have windows and they will work just as well. Once you have captured that idea take a picture with your camera and just wipe it away with warm water, a bit of soap and paper towel. Your ideas now can come to you where ever you are. You can even take them on Holidays. For me I love writing notes to my wife in the mirrors in the bathroom, honestly it sometimes gets a little out of hand, so much fun.