Most in-car portable GPS receivers have a pedestrian or walking mode. The pedestrian mode optimizes the route for walking, and may also adjust arrival times to match walking, rather than driving speeds.
Garmin some years ago released dedicated pedestrian maps for Nuvi devices named cityXplorer maps including Enhanced pedestrian mode and public transit information with 3D builings landmarks.
Unfortunately car devices dont have a battery might support this mode adequately and I think this is the reason Garmin dropped them this year.
Probably these maps would have been more successful if they were supported by handheld devices.
Google, Navigon, iGO, Sygic introduced Pedestrian Navigation in their apps on phones, but IMHO we dont have till now a real dedicated satisfactory, GPS based only, App for Pedestrian Navigation : we have some city guides apps but they need Internet connection via GPRS, Wi-Fi or local network.
It's pity Garmin didnt implemented this mode in its long lasting battery devices .