在谷歌地图上做“路线上的兴趣点”

I need to allow travelers to use google maps to plot a route, and then query my database of points of interest (let's say, McDonald's locations) and then show all of these locations that are within a mile or two of the route they will be taking. The question is, how do I efficiently take the "driving directions" information that comes back from google (essentially an array of lat/long pairs), and turn that into an sql query to get locations that fall within a certain distance from the route?I need to allow travelers to use google maps to