How can I get Google Navigation (navigation in Maps) on Android to navigate walking directions? I know how to get walking/public transportation/biking directions, but driving directions are the only ones I can navigate (tracks the location, shows turns coming up, compensates for wrong turns, etc.).  How can I navigate on the walking directions?

And yeah, I know that I can show the walking directions on the map, and try to follow them myself, but then it's always north up instead of track up and it doesn't make any attempts to snap the GPS location to the street.
Walking Navigation was just released today [Sept 9] as an update to Google Maps 4.5.0