Delivery drivers and urban explorers often waste time finding exact building entrances, alleyways, and hidden access points that main mapping apps overlook.
Develop a crowdsourced app specifically for hyperlocal navigation details, with photos and notes about hard-to-find locations.
Monetize through partnerships with delivery companies and a pro version for frequent users.
MVP could be a simple photo-annotation layer over existing maps.
Risk is maintaining enough user contributions to be valuable in all areas.