While the GPS Heatmap system works surprisingly well, it is not perfect. No program is ever complete. If you're inclined, you might want to consider the following:
Make the road-segmentation algorithm more sophisticated to support one-way roads, and points where two roads intersect but do not join (for example, on a highway overpass).
Improve the route-development process to allow it to capture routes that include U-turns and repeated road segments.
Take the raw GPS data and split it into contiguous segments, process each segment in turn, and then join the processed segments back together again. This will allow the algorithm to work with GPS recordings that include gaps in the recorded data.
Combine the map matching algorithm with a shortest-path calculation to write your own turn-by-turn navigation system.
Look at ways to improve the speed of the map matching algorithm. For example, if two different route candidates use the same road segment, those two candidates should...