By entering what you want to do beforehand, the app would know where you are and have a list of places you said you want to go, and tell you how to get to the next closest place, or alert you if one on your list is about to close for the day. Perhaps each city version is done by locals and in case of bad actors, there can be a voting system so the right info goes to the top. Plus, there could be integration with Google Maps so you can see if you're going the right way.
There's a guy out of Brazil who has a site called Viagens Maneiras (aka Trip to Brazil) and he goes to different locations in Brazil with his dog and takes pictures and offers info on each place. At the bottom of each location page, he has tips listed. These tips are usually comments by his site visitors (on what to do, what not to miss, etc). Anyways, I'm imagining part of his site but with improved functionality and a redesign.
I hadn't visited the site in a long time and it seems to have a few navigational issues (like two-finger scrolling on my track pad required my mouse to be on the text/picture area rather than anywhere on the page).
My original idea was that you do it ahead of time. It would have general ideas of how long it takes to complete an activity and would essentially provide you a list of maps relative to your hotel. Then, you'd have that information beforehand on your smartphone so that you could avoid roaming charges (which is an issue for international travel.)
The revenue model was funneling to travel sites and possibly travel agents who could provide more customized itineraries.
But now, with OpenStreetMap, you could have an app on the phone. On top of it, it could use the GPS to figure out where you were and put together a slide show for your friends. You could rate when you were there and provide more feedback later if you wanted -- just a simple thumbs up/thumbs down.
I've resigned myself to never getting around to it -- If I'm to found a company, it's going to be in the b2b arena instead.
Rather than 'fencing' regions then, if it could be done to just sort proximity that way, it would be incredibly useful even while sparsely populated.
The other issue is what occupies people's hands. It's surprising for me to see how many tourists use traditional maps (though, on the flip side, one never knows when someone is looking at a map on their smartphone), and how many people don't ask passers-by questions in order to get help. A dedicated app would mean less happenstance intereaction while abroad but it would also help not waste time (and give more time for more sights to see).
Another HN commenter mentioned offline capability, in this sense it could be like Wikipedia's make an e-book function, where you'd get, in the case of my idea, the pertinent street view photos, together with the right info downloaded to your phone. For ex, "give me top 10 comments on the Mona Lisa, 5 levels deep and for the Moulin Rouge, which I'm more interested in, give me the top 20 comments, 10 levels deep."
If a 'chapter' is to be added while on your trip, because you heard about something new and cool, then all that's needed is a wifi connection to download the right info and add it to the multimedia 'book'.
I'm not sure, though. The main page isn't clear about what it does exactly, and I haven't created an account.
That said there is definitely something that can be done in that space.
Another useful feature would be suggest me the best food list for the city I should eat.