1) Would be really helpful when moving into a new house. It takes a bit of time to figure out how big the shadows from trees are, how it varies by season, what time a garden area gets shaded by a fence, etc.

I've looked into if there are any sunlight simulators available, but my Google-fu has been lacking. Even if I had a tool that told me "on this date and time, at your location, a 1 meter tall stick casts a shadow _x_ meters in length in _y_ direction", that would be workable.