Hi,
adding a "Take a WLM walk!" function to the app that links
monuments-with-no-photo to Google walking directions? This would be
great to have for "Wiki Takes xxx" meetups during September. The functionality could be based off of the app C:Geo, which is open source.
Related to that, there is a French student project to create an app with overlapping features, called WanderWiki. It is still in its early days, and will definitely not be ready for September, but it might be interesting to you anyway :)
See https://wikitech.wikimedia.org/wiki/User:FatJagm/WanderWiki for more information.