Triptrop NYC is a small mapping application by Jonathan Soma that maps the expected travel time from one point in New York to another using the NY Subway system. Just type in an address and it returns a map with an heatmap-like overlay.
The application uses prerendered images for 128’000 points in NYC plotted on Google Maps. In conjunction with the GoogleBar the user can quickly check for restaurants in 10 minute distance for example. Unfortunately the images don’t rescale thus giving a rather jagged look on higher scale rates.