Or for geospatial purists, via 'satellite navigation systems' for pedestrian. In any case, Slashdot discusses a story named Microsoft Patents Bad Neighborhood Detection.
Their summary: "With the grant of their US Patent #8090532 Microsoft may be attempting to corner the market on GPS systems for use by pedestrians, or they may have opened a fertile ground for discrimination lawsuits. ... Described as a patent on pedestrian route production, the patent describes a two-way system of building navigation devices targeted at people who are not in vehicles, but still require the use of such a device to most efficiently route to their destination. ... For example, the user inputs their destination and any constraints or requirements they might have, such as a wheelchair accessible route, types of terrain they are willing to cross, the option of public transportation, and a way point such as the nearest Starbucks on the route. Any previously configured preferences are also considered, such as avoiding neighborhoods that exceed a certain threshold of violent crime statistics (hence the description of this as the 'avoid bad neighborhoods' patent), fastest route, most scenic, etc."