I went on a walking tour in Columbia last year that was three 3 hours long, I only actually wanted go to a couple stops and by the end of it i was knackered, my girlfriend was miserable and then I was guilt tripped into tipping. Fast forward a year and a buddy and I have built "Roam" and just launched it on android/ios. You can draw an area on the map and it curates a list of possible stops and then allows you pick and choose what you want to see and then turns it into an audio tour ...