The Problem: Thinking of buying a house in a relatively hilly area. It is nearly mid-summer. How can I tell how much sun I will get in the winter.
The Solution: A helmet that combines a GPS receiver, a compass, a level and the ubiquitous small computer. The attached visor or glasses have the sort
of HUD you see fighter pilots using. Projected onto your field of vision would be the path of the sun for a series of days (say every Saturday for a whole year in a constant cycle) along with the date of that path. As you wear the helmet, your position, direction your pointing and the attitude of your head would be used to recalculate the path of the sun within your field of vision. You could then walk around the property and see, for instance, whether that hill or neighbouring house will keep you in shadow until late March.
If instead of just showing the path, a series of suns was projected showing the time, you could also see whether you were likely to get warm long evenings and good sunsets.
I can see many uses for such a device. To find the most suitable place to plant trees and shrubs (not only for their benefit but for the surrounding area). For the design of extensions and alterations to houses.