walkscore can already map out all "within walking distance of grocery + rail" locations in Portland (and elsewhere). E.g. http://www.walkscore.com/apartments/se

walkscore can already map out all "within walking distance of grocery + rail" locations in Portland (and elsewhere). E.g. http://www.walkscore.com/apartments/search/Portland-OR?zoom=12&sort=14_low&hood=off&nearby=%7B%7D&places=%5B%5B%22Groceries%22%2C%2210%22%5D%5D&transit=%5B30%2C%2219.81.83-85.99%22%2C45.537169%2C-122.65015900000003%5D&lat=45.535517621410435&lng=-122.64287605285642 http://www.walkscore.com/apartments/search/Portland-OR?zoom=... The actual scores would have to be looked up one at a time, on per-address basis (e.g. http://www.walkscore.com/score/320-pioneer-way-mountain-view-ca-94041 http://www.walkscore.com/score/320-pioneer-way-mountain-view... )