Google Maps recently added walking directions. And it works great. It ignores one ways and uses pedestrian bridges wherever possible. Check out these screen shots, which show driving directions (left) and walking directions (right).
The above directions are from the University of Montana to the Albertson's shopping center which is located north of the Clark Fork river. When walking directions are chosen, Google Maps correctly shows the shortest path as the one taking the pedestrian bridge across the river.
Check it out for yourself at this link: Directions from UofM to Albertsons.