Just checked out Easy Measure and was wowed by the coolness:
EasyMeasure shows you the distance to objects seen through the camera lens of your iPhone or iPad. Simply aim your iPhone/iPad to any object in your surroundings, and EasyMeasure displays the distance towards that object on top of the camera image. With its amazing 3D camera overlay grid, using EasyMeasure is very intuitive and easy!
Not sure how I would use this, but now I want to measure the distance between things- room measurements, perhaps?
A very useful list of apps, perfect for use the classroom!