An idea for an app for runners: It asks how far you want to run, e.g. A marathon, over how many days, e.g. 30, and then plots a circular route on Google Maps for that distance. And if you miss a run it would spread that missed distance out over the remaining days. It could even allocate the distance to be run each day on a curve so that you start with a smaller distance and go further each day and by the end of the time period you’ve covered the total distance.