This is the sort of new idea that could and really should take off more so than it already even has. Airports, lobbies of hotels, bus depots, train stations ... businesses that cater to people who have just arrived in an unfamiliar place and need some info on travel to meetings, etc.
The bitch of it is it's computationally intensive; there are a few places online where you can generate them yourself using Google's API but the two approaches are: 1) Set up your map, break it into grids, and calculate travel time for every pixel in that grid. A 100-pixel grid around my house for five miles took 10 minutes to generate (a 3000 pixel grid covering central asia took 20... says something about roads out there, or about Google's data) 2) Set up your start point and drunkard's walk your way down every road you see, stopping when you hit your predefined limit. Of the two sites I found that do this, neither of them complete - I suspect Google has set up a "quit hammering our servers for calls this way" filter. I found a couple services that have software that allows you to do it. One of them wants 800 euro a year for a license. The other wants 500 for a coords-in, coords-out no GUI codebase. Fun to play with, though. Too bad I don't have a spare Beowulf cluster sitting around.