I mapped what's within walking distance for European cities using OSM
Hex-grid walkability scores beat Walk Score's coarse neighborhood averages.

Crowdsourced surveillance camera map on OSM—view, edit, and contribute locations freely.
Privacy advocates, journalists, activists, and concerned citizens
Überwachungskarte · MapComplete · OpenStreetMap
Hex-grid walkability scores beat Walk Score's coarse neighborhood averages.
Live Istanbul transit map is useful locally but lacks novel tech or broader appeal.
It actually does a concrete, unusual thing: edit PBFs to excise roads exposed to ALPR and then produce an OBF for offline routing in OsmAnd. The implementation leans on pyosmium/osmium-tool (the tricky bit is keeping PBF integrity) and ships as notebooks + a demo OBF, so it’s immediately useful to tinkerers but lacks a user-friendly pipeline or GUI for non-technical users.
Curated OSM mapping hub for power grids when JOSM already handles the actual editing.
No-key OSM wrapper with built-in MCP server beats Google Places on price.
Clean crime map but Citizen and SpotCrime already do this with more data.