The only real "problem" with UWB is the range. It might work better in North American homes (with hollow drywall walls), but in my Spanish home with brick interior walls, UWB doesn't even work one room over. It'll say "nearby", but completely lack any sort of direction information unless in the same room. I'd suspect in a situation like the OP was in in Paris, it would be very difficult to distinguish and exact location using UWB unless you got really lucky (like the phone was being stored directly next to an exterior door or something).