Hi Alice,
Thanks for posting.
Your app does look interesting. I think it will most likely have the greatest appeal to the new hiker(s), unfamiliar with the trail. Of course this may be the largest demographic, so for you a good thing smile . I guess your pictures, and progress reports will give them comfort as they make their way up the trail. For those who have hiked it previously I doubt it will be used or needed (unless they make the hike in the winter – and I guess this is a small number of people). They know that the main trail would be difficult to get lost on in summer, so except as a convenient mechanism to keep track of their progress I'm not sure it will be used. The more experienced hikers/mountaineers may spurn the use of these new fangled gadgets. Perhaps similar to the time when calculators were not allowed in school. You just got to do it by hand. Not saying that map reading and route finding skills are not good to have. Just not needed for the main trail of Mt. Whitney (in the summer).
Lots of other day hikes you could do. What other hikes are you considering?
Regards,
John