Today’s invention is based on people in wheelchairs carrying with them smartphones which can record or transmit their location.
These data would reflect, over time, those routes and destinations that enabled wheelchair access and could be overlaid onto eg Google StreetView (especially future versions which map the interiors of public buildings).
Areas which failed to be mapped would highlight regions from which wheelchair users were possibly being excluded.
It would be pretty easy to use software to automatically identify eg U turns as locations where wheelchair users had been thwarted. Perhaps it would also be possible to ask people to do a special spin or X gesture there to highlight a problem.