Potential Idea :
As a part of my gsoc project I was thinking of developing a cross platform mobile+web app (or atleast for android) for the wiki-maps( apart from replacing the web map-widget with the one made using leaflet).
I'd already built an (as a part of my sem project) which used osm and leaflet to render/show the map on the mobile device(it was an offline app made for routing and searching).
It would be an online app with which the user would be able to view the map and the add the new push-pins to the map (with better UI ie user need not enter the coordinates of the location instead the location could be fetched using the inbuilt gps of the mobile) . I think I would be able to make such an app in the given time period because of my prior experience.
Potential Challenge :
The only challenge would be sending and retrieving data from the wiki-server. For that I would require a little assistance from your side as I'm not familiar of how to the wiki-server works.