I've wanted something like this - in Boulder the foothills cast a shadow on the town considerably earlier than sunset provided by weather apps. So in theory, this should be possible to figure out when a park will actually see a sunset. Nice work!
One of my favorite apps is PeakFinder, it shows local topography in an AR style UI. It also shows where and when the sun will set given the mountains around you! Well worth the few bucks.
Definitely one of my favorites too! In my experience though it's best used at the location you're expecting the sunset, tricky to see when a specific point elsewhere will have their sunset (it may have changed though, I should check this)
